Effective Health (henceforth EHP) is a measurement of how much raw, unmitigated damage you can receive before dying. It is an important stat to know and keep in mind when deciding how to gear your character. How it is calculated varies from game to game, but at its simplest it is Health * (1 – %Mitigation) = EHP. Being an old theorycraft buff from a game which shall not be named, the moment I saw how simple GW2’s damage formula was I simply had to get my fingers in there and figure out exactly which ratio of toughness to vitality yields the most EHP possible.
After some work at it, here is the formula I ended up with:
V = (10D + 10S – B) / 20
- V is the optimum amount of ADDITIONAL vitality you should itemize for out of S stats.
- D is your base defense from gear and traits (with level 80 exotics that is 920 for light, 1064 for medium, and 1211 for heavy armor. Add 61 if you use a shield.)
- B is your base health BEFORE vitality is factored into — being again, health from traits plus base health (1545 for elementalists, guardians and thieves, 5922 for mesmers, engineers and rangers and 9212 for warriors and necromancers.)
- S is the amount of stats you’re willing to put toward EHP. This amount is set by you, the user of the formula. If you want to use 1k stats for EHP, then put 1k in for S.
Some notes about the formula:
- This is just a measure of EHP. This doesn’t factor healing or Healing Power in at all. However, you can put it in there if you want — take a rough guesstimate of how much healing you expect to get throughout a fight and add it to B. Let’s say, as a mesmer, I expect to use Ether Feast twice in a fight, I’d just take double what my Ether Feast heals for and add it to B.
- This formula gives you the ideal mix of vitality and toughness that grants you the highest possible EHP. The formula, however, outputs in terms of V, so if you need to get toughness, just take the output and subtract it from S, which is the amount of stat points you’re spending on both toughness and vitality.
- For low quantities of S you will usually get a V which is larger than S. This is okay; all this means is that if it were possible the ideal spread of vitality and toughness actually involves dropping below the base toughness amount, which clearly isn’t possible. The opposite is true if you get a negative V somehow — that means the ideal amount of stats involves so much toughness it’d be best to below minimum V. In either of these cases, just go full toughness or vitality.
So how about some practical results and examples?
Let’s say I’m playing my mesmer, which is almost always true. Let’s say I’m in WvW, running a build with 20 inspiration (vitality and healing power) so I can get that delicious Warden’s Feedback trait as well as 20 points in Chaos (toughness) to get the 20% faster staff skill recharge. Let’s say I expect to cast Ether Feast once before dying, but don’t expect to get any benefit from the additional illusions because those guys have the lifespan of a microbe in WvW. (Also assume no healing power on gear, for simplicity’s sake.) And finally, let’s say that I’m going to itemize my gear so that I’ve put 500 stat points into toughness and vitality — I don’t want to to an undying juggernaut, but I’d like to not explode when someone looks at me either.
So let’s get into the formula. My D is going to be 920 (full cloth exotics) + 200 (from 20 points in Chaos), or 1120. My S is 500, as I set it in the last sentence. My B is going to be 5922 (mesmer base health), plus 2000 (vitality from the Inspiration trait line), plus 5760 (the value of one cast of Ether Feast), or 13682. Now put it together:
V = ( [10 * 1120] + [10 * 500] – 13682) / 20
V = 125.9
Of my 500 stat points, I should make 126 of them vitality and the other 374 points toughness so I have maximum EHP under this scenario. Important — and good to know.