Mutilate spec for Heroics ...Follow

Energy pooling is for specific points in Mutilate cycles. You're dealing with different timers which aren't exactly in synch over a boss fight. There's a spot where the different timers hit the same "beat" every once in a while and you need to pool energy for the next barrage. Generally you pool before starting in on 2 Mutis after landing a Rupture and with plenty of time left on HfB. But there are other points as well.

No talent is really despised. They're either optimal for min/maxing or not.

Also note that energy regains with time. So that even with 100 energy getting off 2 mutilates barely loses time between cooldowns.