While we're on the topic of 'overpowered', here's some food for thought. It's my firm belief that Quag's Eye offers a more signifigant DPS boost (at least for destro warlocks) in a fully buffed raid environment because of the addition of flat modifier (the 37 damage taking advantage of the 30% in modified damage of debuffs) and the 3 shadowbolts/incinerates that can be cast in the time span that 2 can normally. I guess what I'm saying boils down to is that it looks like quag's eye might scale faster than the capacitor. Then you can always throw in some bloodlust for a bit of fun ..
Quagmirran's Eye + Bloodlust =
imbalanced cast rate
The only problem is that capacitor *can* be quantified through damage meters while it would be very hard to fully do so w/ the eye.