Epic Resurgence lets you recover the use of an encounter power.
The first time you score a critical hit during an encounter... If you use an attack that targets multiple foes, you gain this feat's benefit only on the first attack roll you make.
Does this mean if you attack with say twin strike, and crit with the second attack it doesn't trigger the Epic Resurgence? What if both attacks are on the same enemy?
Twin Strike is actually two attacks:
Attack: Strength vs. AC (melee; main weapon and off-hand weapon) or Dexterity vs. AC (ranged), two attacks
Which means that a critical hit on either of them would be eligible to trigger Epic Resurgence. Contrast that with Sweeping Whirlwind, for example, which makes a single attack against multiple foes. Only the if the first attack roll you make is a critical can you take advantage of Epic Resurgence.
The intent is to limit the ability to trigger the feat by making area attacks that include large numbers of opponents using one action; powers such as Twin Strike that let you make multiple distinct attacks as one action are typically limited to two or three attacks at most. At the extreme other end, consider something like Cloudkill, which as an Area Burst 5 could make at least one critical hit remarkably likely.
My understanding of the last phrase means that you only activate the power on the crit roll and not on the number of targets that the crit roll is applied to. Meaning, anytime you roll a Crit you get to use this power only once. It does not matter what order you make your crit rolls in.
It simply means that if you roll several natural 20s on a burst or area attack, it will not give you several encounter powers back.
