Survivability in Diablo 3 takes in account 2 components : toughness, and healing. While those stats are easy to understand, the mechanic behind and between them and how to take profit of both is not always obvious. I'll try to explain to you how to take advantage of the different affixes you have in the game in order to become really survivable and have a great sustainability.
Toughness represents (if you read the tooltip) the number of damage your character car undergo from full life to zero.
While it's clear what toughness is, it's harder to understand how to optimize it. A common mistakes is to have a really high life pool (lot of vitality) and overlook armor and all resist. While your sheet toughness will look the same, if you don't have enough resistances and armor, your life pool is just a big amount of lie. It provides a fake sense of toughness when you can actually die really easily.
Toughness is a balance between Vitality, Armor and All Resistance. To reach Higher Torment difficulties (and especially Torment 10), you will need at least about 800+ All resist, 15 000 Armor and a life pool of ~600 000. With a Demon Hunter, you can boost up those stats with your companion Boar and with the passive skill Perfectionnism. Last but not least : the more Life you have, the less the healing stats will be effective, that's what I'm going to explain in the next section
Healing and synergy with an optimized Toughness
Healing affixes are : Life on Hit, Life after kill, Life per second and Life per resource spent (The latter exists only for melee classes). Why are those affixes important ? It's easy to overlook the healing stat by thinking that health potion and health globe are enough. While they offer you some good sustainability, the drop rate of globe and the cooldown on the health potion doesn't make them as reliable as other Healing affixes.
Let's take a quick example by comparing 2 situations:
- 5M toughness
- 30 000 HP regen/sec
- 500 000 HP
- 5M toughness
- 30 000 HP regen/sec
- 300 000 HP
They have the same toughness however B has 200 000 less HP which implies more armor and/or all resistance: but why does it matter ?
Let's assume both are being hit by a monster that deals 500 000 damage per second. It's 1/10th of their toughness which translate into them losing 1/10th of their life pool per second. For A this represent 50,000 HP and for B 30,000. However, both heals for 30,000HP per second... see where I'm going ? Indeed, in this situation B will never die while A loses 20,000 HP per second and die after 25sec. Of course in the game you are facing way more factors than just one monster hitting you but you get the general idea.
The trick is to understand that healing give back raw HP and not toughness, so depending on your life pool : you are getting back a better % of your toughness if you have few HP but High Armor and All Resistance. For A each life point account for 10 toughness and for B each life point account for ~16.5 Toughness which makes the healing stat about 65% more efficient for B.
You now understand that healing can be very powerful, you should use :
- Life on hit when you have a high attack rate or you are using a skill that have a high proc rate.
- Life after kill allow you gain huge amount of life when clearing trash mob (if you have powerful AOE, this stat does wonder).
- Life per second offer sustainability during the whole fight (you can gain it easily with Paragon point or with the Templar compagnon when playing Solo)
- Life per resource spent if your character benefit from it.
Survivability is a mix between killing fast, toughness and healing. for the defensive aspect, the more you stack Armor, All resistance (and damage reduction modifiers), the more powerful your healing becomes so you can survive much longer even with a smaller toughness number. What you get with this sense of "false toughness" when stacking a lot of vitality is actually "diluted healing".