Fel Stamina

Fel Stamina was a talent in the Demonology tree, you would need to spend 13 points in Demonology to max it.

4-5 ranks can mean 1-2 more hits required to kill your Voidwalker up until the end-game instances. When combined with 3 ranks of Improved Voidwalker it actually makes him an excellent soloing tank so long as you don't spam shadowbolts from the outset of the fight.

5 ranks will make a serious difference in the staying power for your Felhunter when you're fighting higher-level caster mobs because more HP means it will take them more spells to kill him, which in turn gives them more chances to re-cast their defensive spells which Felhunters love to devour.

The Succubus and Imp won't get as much out of this talent as the other two. They benefit more from Fel Intellect than Fel Stamina.