Shield healing is one of the things that sets Medics apart from the other two healing classes (along with, of course, having by far the coolest weapon). In this post I want to look at Shield Surge Tier 4, whose major upgrade increases shield mitigation by 25% for 8sec. However, this will first force us to take a careful look at shield mitigation and the general tradeoffs between shield healing and health healing. If you have a firm understanding of shield mitigation from my earlier posts, you can skim/skip the first section (although you will miss the cool graph).
By default, shields take 50% of the incoming damage and pass the other 50% through to health. The passive part of a Medic’s innate (Energize) gives a 15sec buff that increases shield mitigation by 25% whenever you land a shield heal. So provided you are regularly casting Shield Surge, a Medic’s target will likely have a “base” shield mitigation of 75%. The Buffer buff from Shield Surge T4 will take this to 100%.
There are still some comments on the official forums and elsewhere that talk about shield healing being only 50% (or, including Energize, 75%) “as effective” as health healing, implying that the shield mitigation number in some way translates directly into how “good” shield healing is relative to health healing. This is simply not true, as I argued in my first post, shield healing is almost always just as good as health healing, even when shield mitigation is less than 100%. By “as good as,” I am using a metric of how much damage the target can take before dying, which I will call “Effective Health” (EH for short). Now, “almost always” is not always, and I will explain the exceptions to the general rule below.
At the risk of belaboring the point, here is a little thought experiment that drives home the central idea from my original post:
Suppose a player has 1,000 health and no shield. You would say she has a health pool of 1,000. Now imagine something (say an add-on) always colors 50% of the remaining health bar Green and 50% Blue, no matter what the total remaining health. Initially she has 500 Green Health and 500 Blue Health. What happens as she starts taking damage? Well, if she takes 100 damage, she is down to 900 total health, 450 Green, 450 Blue. If she takes another 200 damage, she is down to 700 total health, 350 Green, 350 Blue, etc. The Blue Health pool is absorbing 50% of the damage and passing 50% of the damage through to the Green Health pool. Note this is absolutely identical to a player in WildStar with 500 health, 500 shield, and 50% shield mitigation. So saying shields are not a “real” health pool at 50% mitigation is equivalent to saying the “top half” of a player’s remaining health bar isn’t “real” health because it only ever absorbs half the incoming damage (passing the other half through to the “bottom half” of the remaining health bar).
So even at 50% mitigation, shields are equivalent to health? Most of the time, yes, but not always. They are equivalent in the above analogy because we never considered healing (or other means of hit points regenerating), so the remaining shield (i.e., Blue Health) was always exactly equal to the remaining health (i.e., Green Health). The equivalence is broken because you die when your health is zero, no matter what your shield is. This brings us back to the concept of Effective Health, which is defined as “how much damage can the target take before dying.” If the target has current health H, current shield S, and shield mitigation M, then Effective Health is:1
If the ratio of current health to current shield, H/S, is above this “breakpoint,” (1 − M)/M, then Effective Health is just the sum of current health and current shield, which makes intuitive sense. In these cases, you won’t ever die with your shields up in the next hit (after the next hit, we would need to reevaluate if H/S was still above the breakpoint or not). If the ratio of current health to current shield is below the breakpoint, Effective Health does not depend on the current shield level S. This is because we are in the zone where the target’s health is low enough that she can be killed in the next hit while still having some shields left. If you are in this second case, or more correctly, if you will be in this second case (H/S < (1 − M)/M) after the next Shield Surge you are thinking of casting, you might want to rethink it because that additional shield will not move your target any further away from death (i.e., it will not increase her Effective Health at all), whereas a health-heal certainly would.
Since we are approaching the 1,000-word mark, it’s time for a picture. Let’s imagine a target whose max shield is 30% of her max health, which I believe is a pretty representative value. The plot below shows the possible values of the target’s current Health percentage (x-axis) and current Shield percentage (y-axis). At any point in time, the current state of the target corresponds to one point in this (unit) square. Given the Effective Health discussion above, we can divide this square into regions where shield healing is useful for increasing Effective Health, and where it is not. I will assume a mitigation value, M, of 75%, which represents the “typical” shield mitigation for a target who is being frequently (at least once every 15sec) healed by a Medic (without Shield Surge T4). The green region is where shield healing is as effective as health healing in increasing Effective Health, and the red region is where it is not.
Note the only assumptions I’ve made are the ratio of max shield to max health, and the shield mitigation percentage. The triangular region where shield healing is ineffective is pretty small (for the geometrically inclined, it’s just 5% of the area of the square). The implications of this for Shield Surge T4 will be discussed below. One final caveat: we have ignored overhealing considerations in this discussion. For example, if you are deep in the green region above, where shield healing is effective, it still might be better to cast a health heal over a shield heal if the target is at 95% shield and 50% health. But hopefully that is obvious.
Shield Healing vs Health Healing
Before delving into Shield Surge T4, let’s discuss a couple of basic things about health healing and shield healing. First, in general, shield healing is less Focus efficient than our “baseline” health healing abilities. The table below compares Healing Per Focus (HPF) for our primary shield heal to some of our health heals, assuming a level 50 Medic with 2,000 Support Power, 20% Critical Hit, and 175% Critical Severity healing a single target.
|Shield Surge T4
|Shield Surge T4 w/Reboot
|Mending Probes T4
The healing abilities I’ve included for comparison are what I believe are typically used to do the bulk of baseline health healing on a target taking sustained but not spikey damage (e.g., the tank in your 5-man taking mostly white hits from a trash pack)2. We see Shield Surge T4 is only about 30% as efficient as Emission T8 and Mending Probes T4 without Reboot, and still only around 65% as efficient with Reboot.
Of course, the compensation we get for this lack of Focus efficiency is shield healing allows us to effectively maintain our target’s Effective Health at a significantly higher level (around 30%) than we would be able to if we didn’t heal shields at all (in which case they would very quickly be gone, and on a tank, highly unlikely to ever naturally regenerate during combat). Maintaining a higher Effective Health makes overall healing easier because it gives you more of a buffer to deal with any combination of: a) damage spikes on the target (via mechanics or player mistakes), and b) being unable to heal the target for a period of time, either because of range issues, cc issues, or you being away healing someone else (or prying the cat off your keyboard).
So to review: shield healing, even with Reboot procs, is less Focus efficient than our baseline health heals, but it helps maintain a higher Effective Health, which can be hugely beneficial.
Shield Surge T4
We are finally in a place to take a good look at Shield Surge T4. I am going to focus attention on situations where the Medic is the only healer present (e.g., 5-mans), and hence the primary source of all healing. Assuming Shield Surge is cast regularly, Shield Surge T4 increases shield mitigation from 75% to 100%. This has three major effects:
1) It makes shield healing always useful in increasing Effective Health. In the graph above, the red region disappears; at 100% shield mitigation casting Shield Surge will always increase Effective Health even if your target is at 1% health, since it is now impossible for them to die with shields up.
2) It makes shields deplete faster by 25%, since they are taking more damage. If the rate of incoming damage was such that the shield was broken in 4sec by incoming damage, it will now break in 3sec. This means that to maintain shields, you will be casting Shield Surge more frequently and likely procing Reboot more frequently.
3) Until the shield is broken, there is no damage to health. This means that Emission, which we need to cast at some point to build Actuators for Shield Surge is going to be 100% overhealing except for the damage that gets through in between the time shields are gone and we Reboot them.
The first effect is unambiguously a positive, but how big a benefit is it? It will help when your target is at very low health, but hopefully you seldom find yourself in that spot. Of course, even if it only helps once in a dungeon run, it may be the difference between a wipe and a kill (or a medal and no-medal), so just because it doesn’t make a difference often doesn’t mean it can’t make a big difference.
The net effect of the second point is a little subtle and depends on your Shield Surge strategy. We will consider two cases: casting Shield Surge only when Reboot will proc, and casting Shield Surge whenever it would result in zero overhealing. The second strategy is clearly more Focus intensive but maintains a higher Effective Health. In the first case, 100% of your Shield Surge casts will proc Reboot (by definition), and therefore the only difference between Shield Surge T4 vs not T4 is casting more often and hence burning more Focus. For the second case (Shield Surging as often as you can without overhealing), I’ve run some simulations and it again appears T4 results in a higher Focus burn rate (the cost of more frequent casting negates the “savings” from a higher percentage of Reboot procs).3 How much higher depends on how much effort you put into maintaining a high amount of shields, which will of course depend on whether you are trying to prepare for a damage spike (or just the unexpected).
The third effect is really the flip side of the second: in addition to spending more Focus on less-Focus-efficient shield healing abilities you have less opportunity to leverage the efficient health healing from your builder, which again, you have to cast at some point for Actuators, whether there is a health deficit or not.
Bottom-line, I think Shield Surge T4 hurts Focus efficiency in exchange for eliminating the “red zone” in the graph above, making shield healing always useful for increasing Effective Health, even on very low-health targets. It also costs 5 (or 8, depending on how you count) Tier points, which are certainly a precious resource. On balance, is it “worth it?” I think that is open to debate, but I think it is less useful than some people seem to think.
- Shield healing is almost always just as effective as health healing in terms of increasing Effective Health, even without the Tier 4 major upgrade from Shield Surge. The exception is when the target is below around 10% health, in which case there is a danger of them dying with shields up in the next hit.
- In general, shield healing is great because it allows Medics to increase the maximum Effective Health of their targets, but at the expense of being less Focus efficient than our baseline health-healing abilities
- If you spend Tier Points for Shield Surge T4, you are reducing your Focus efficiency in exchange for making shield healing effective on low-health (< 10%) targets. Whether or not that is a good trade is debatable, but that is the trade.
1 The term “Effective Health” is often used in a different context, combining the size of a health pool and damage mitigation percentages (e.g., armor, resistances, etc.) to allow one to compare the tradeoffs between increasing the overall number of hit points and damage mitigation stats. In the context I am using it, I am ignoring damage mitigation since health and shields are both subject to the same damage mitigation stats (as far as I can tell). So mitigation doesn’t impact the discussion above at all; if you like you can assume all the damage I am talking about is “post mitigation.”
2 Additional assumptions made: you are above 250 Focus, so the T4 major upgrade on Emission is not triggered, you are triggering the Emission T8 major upgrade 80% of the time, and Mending Probes are not detonated.
3 To get some idea why this is the case, we need to rock a little math. Let S be the healing of an average Shield Surge, R be the amount of healing done by Reboot, xT3 and xT4 be the fraction of Shield Surge casts that proc Reboot assuming T3 or T4 Shield Surge, respectively, and cT3 and cT4 be the rate of Shield Surge casts per second assuming T3 or T4 Shield Surge, respectively. In the T3 case, the shield HPS is cT3*(S + xT3*R), and analogously for T4. Now, in steady state (and assuming no overhealing) the shield HPS has to be equal to the incoming shield damage rate, and given shield mitigation is 75% for T3 and 100% for T4 we must have cT3*(S + xT3*R) = (75%)*cT4*(S + xT4*R). We are interested in cases where cT4 < cT3 (i.e., we are casting Shield Surge less often with T4), which implies (after some algebra): xT4 > (1/3)*(S/R) + (4/3)*xT3. Using the known values for S and R (and taking into account the fact that S is a little different between T3 and T4), this becomes xT4 > 27% + (4/3)*xT3. So for example, if you were getting 25% (= xT3) of your Shield Surges procing Reboot with T3 Shield Surge, you would have to get 27% + (4/3)*25% = 61% of them procing at T4 (assuming the same rate of incoming damage) to net be casting Shield Surge less often and hence burning less Focus per second. This is a high hurdle to overcome without resorting to only casting Shield Surge when Reboot will proc (in which case xT4 = 100%), but that contradicts our assumption that you were casting non-Rebooted Shield Surges to maintain higher Effective Health.