“when you hit an enemy you have 100% chance to inflict a future attack 2 seconds later that deals 50 damage”
if you unequip all gear then the damage done is roughly in line with 50 void damage +X% void damage (x being whatever you have in +void).
When you then put all your gear back on the damage increases but not enough to be void damage +stat for the skill that procs the future strike (so strength if you proc from melee and attunement if you proc from devouring orb)
its unclear if the output damage on future strike is being calculated correctly or what is actually going in the calculation and the numbers dont come out at what is expected when you manually calculate it.
So I did some testing, my character has:
+109% void damage
25 strength (+100% damage for skills that benefit from strength)
23 attunement (+92% damage for skills that benefit from attunement)
+40% global damage from Devouring Orb (if it’s running)
Future strikes does 50 void damage, therefore if it’s proc’d from the basic attack I would expect it to do ~105 damage.
Attacking with the basic attack (no Devouring orb) I got 40 (non-crits) with an average of 105.6, min 84, max 125 which agrees very well to the calculation (50 * (1+1.09)) = an average of 104.5.
Attacking with Vengeance (which benefits from strength) with no Devouring Orb I got an average future strike damage of 159, min 125, max 185. This is broadly in line with future strikes being effected by void damage & the stat for the skill that procs it (str in this case) for a calculated average damage of 50 * (1 + 1.09) = 154.5.
Using Devouring Orb I got an average of 169.7, min 126, max 205. Which is in line with future strikes being effected by void damage, the stat from the skill (attunement in this case) & global damage, all being additive (50 * (1+ 1.09 + 0.4 + 0.92)) = ave 170.5.