borderlands-2
The Assassin/Zero's Resurgence skill restores health with melee kills depending on his own health. How do the health benefits scale with your health? What constitutes "low health" for the purposes of getting the maximum 4% life return on a melee kill?
I initially guessed 50% health was considered "low health." If you were to melee attack light enemies (i.e., non-heavy enemies like most Bullymongs) at 50%, it would cause them to stagger. Though after experimenting, this doesn't seem to be the case.
Based on my observations, I'd say "low health" is ~33% health (or 1/3 health).
Fortunately, it is pretty clear when the ability was applied in a kill. Normally you deal a fixed amount of damage to everyone. When the ability is applied, you see a boost in the damage dealt and you get a nice "buzz" sound and a slashing animation for every hit.
To test this, I respec'ed Zero and went off to fight making sure I didn't level up any more during the tests. As a baseline, I fought off enemies with only the Deception skill and no other skills. Every melee attack I dealt gave 55 damage.
I saved and restarted to go on another run. This time I added Killing Blow Level 1 to the mix. Again, most hits dealt 55 damage. Using a weak gun, I chipped enemies' health to around 50% (as close as I can get it) and hit them with a melee attacks. Still did 55 damage. I then tried for 25%. Again, as best as I can, I chipped them down to as close as I can to 25% then hit them with a melee attack. I got boosted damage and other indicators of a successful hit. So it's definitely applied at least at 25%.
However I noticed that at times when I wasn't quite at 25% but a little higher, I was still able to get the successful hit. So apparently it was higher. After a few more tests, I came to the conclusion that it is at 33% at max.
To see if the level of the skill affects this, I tried again with Killing Blow Level 2 and up. You get even more damage of course but it still seemed to apply at 33% and didn't change.
The intent of Terramorphous is to be a raid boss, something you bring 4 players along to fight at once. It's possible to beat him with a coordinated team, good equipment, proper skills and tactics (or a reasonable combination of the above), but there's a super cheap slightly helpful way to beat him even solo, too.
With The Bee shield and the Conference Call shotgun, Terra is trivial. The Bee adds 40k-50k extra damage per bullet, meaning any good shotgun can do over 500k damage to Terra in one shot. The Conference Call shotgun is optional, but shotguns are best for this method, and the Conference Call is ideal.
The Bee has been significantly nerfed in a recent patch (actually all Amp Shields were) so the amp damage no longer applies to each bullet from multiple bullet weapons (shotguns); instead the damage is split across all projectiles. This means shotguns went from insanely broken with The Bee to being only minorly boosted. Instead try a high Rate of Fire weapon that shoots single bullets per shot (or that fires pellets so close all of them will hit).
You can get The Bee from Hunter Hellquist.
Rapid Fire guns like SMGs work very well. If you can boost shield recharge rate at all, do it; you'll want your shield charged as often as possible, the Bee only kicks in at max shield.
Killing Terra is much harder than it used to be with The Bee but it's still a relatively quick way to do it. The more the merrier though; a team is now almost required so see the tips below rather than hoping on soloing him.
Like the mission description says, You Will Die. Even if you take the cheap route, this boss can kill you with a flick of his wrist (tentacle).
This should go without saying, but it's vital. Terra will always spawn at level 50-52. You deal decreased damage to targets higher level than you, so even if you have The Bee and amazing weapons, your damage will be drastically reduced if you're level 45 and Terra is level 52. Save this fight for after your second playthrough to save yourself a lot of grief.
Everyone should use headsets if possible. You don't have time to type (don't try, you'll get killed and piss everyone off), use headsets or just play in silence. Coordination is key for doing things live reviving allies
Lots of skills are useless in this fight. Kill skills aren't great (but you will have tentacles to kill), anything that requires multiple kills isn't great. Elemental damage isn't helpful. Abilities that benefit your team over yourself are often helpful, like the ability that turns Phaselock into an instant revive. Note that no part of Terra can be phaselocked, so keep Phaselock for Revives. Use Decepti0n to trick Terra while reviving allies.
There's a cliff face on one side of the arena; all players should gun this wall unless running from an attack or grabbing ammo/health (tentacles drop a lot). Spread out a bit so he can't kill you all at the same time. Standing high on the outcropping near the wall will avoid Terra's direct attacks. There's also a little niche where one player can hide from some tentacle attacks. If you don't hug the cliff, Terra's knockback can often knock you off the edge of the arena for an instant kill.
Like Crawmerax before him, Terra has a slow elevator leading up to him. After being used it takes a minute or two (seriously, not "a few seconds" or "a little bit") to shoot all the way up. If two players die, make sure you both get on the elevator at once or one of you will be waiting a long time to get back in.
Get back in the fight as soon as possible though, as soon as no single player is alive (or in Fight For Your Life) in Terra's arena, his health resets to max. Be quick but be reasonable; if another player is about to die, wait a couple seconds for them to spawn and use the elevator together. Buy ammo if absolutely necessary, but remember his tentacles drop lots of ammo anyway.
Terramorphous is occasionally elementally charged and will resist the element he shows up as; I've seen him as Shock and Fire, not Corrosive yet but I'm not sure. It's best to not bother with elemental guns, he doesn't appear to take Damage Over Time damage and doesn't seem especially weak to anything. Sirens should spec away from elemental damage.
Terramorphous can occasionally be slagged but he usually resists it. When he's slagged it lasts for about one second instead of 8, so don't bother unless your best gun is already slag.
Obviously use your best guns. Don't use elemental guns hoping they'll do DOT, but he does seem to take elemental damage normally. There's no particularly fancy strategy here, put a lot of very big bullets into him. Bring different kinds of guns or you'll run out of ammo. Bring at least one long range gun for the tentacles.
Being a Thresher Terra moves a lot and has many relatively small crit spots, so sniping can be trickier, but due to his bulk his crit spots aren't too small.
The tentacles he spawns can be annoying, but they're great for Second Winds. Generally it's best to just wound them or ignore them, depending on type, and use them for a Second Wind if someone is knocked out. Hurting tentacles hurts Terra, too, but unless you're sniping you're likely to miss the tentacle a lot more than Terra itself.
Note tentacles drop lots of health and ammo though, so kill some just to keep everyone full of ammo.
Terra drops a lot of whites and greens, a few blues, a couple purples and always drops one orange class mod (it's not as good as you might hope), and apparently has a chance to drop other orange weapons.
Unlike Warrior, Terra drops all his loot in a tight circle around where he dies. There's pretty much zero chance his loot will fall off the map or be stuck in his body, making the looting much less frustrating than Warrior or BNK3R. You can also see all of the items at once, so there's less risk of ninja-looting ("oranges? There's no orange guns over here....")
I'd say Terra is easier than Crawmerax, even ignoring The Bee trick, and certainly less frustrating to fight. His tentacles will rarely kill you unless you fail to evade, as opposed to Craw Maggots which would zip in, kill you, and flee out of range. Getting second winds is easier, and you don't have to worry as much about elemental matches with the minions. The lack of specific weakpoints you have to kill, one by one means it's much easier to hurt Terra; just shoot in his general direction. He soaks up a lot more damage, but it's much easier to hit him.
If player respawns are spread out, getting back into the fight isn't quite as long or annoying as the infamous Crawmerax elevator. And he doesn't drop 50 %$^&ing equalizers every time he does. Generally he's still extremely hard like Crawmerax, but not frustrating. The only annoying "Crawmerax" thing Terra retains is the instant-kill attacks and knocking players off the map (instant kill without a chance to revive!).
Best Answer
You are, effectively, healed for a percentage of your missing health. Level 5 resurgence restores 20% of your missing health. So say you are damaged to 50% of your maximum health; killing an enemy with a melee attack would then heal you for 10%, putting your health at 60%. Alternatively, if you activate resurgence while you are at, say 10% of your health you will be cured back to 38%.
MBreadley's formula is correct.