So with that student of Caiphon feat, does it have to be a power that targets multiple creatures, or just one? If its one, that's hokey overpowered. For a bit of damage which is easily fixed, I gain reliable on all of my powers.
E.H. When you realize just how much damage you are doing, it seems a bit more reasonable. A full attack from a high level solo isn't expected to break 27 DPR. And this will give you 27, 23, 11, or 17 pretty easily if you miss.
Now, at level 1-7 its pretty darn good. But don't expect to be using it a lot at higher levels. That and, warlocks have terrible DPR anyway, so boosting that isn't exactly something to worry about.
The Real Problem is twofold Pact:
Or, Every warlock has to be a tiefling because ha, ha, screw all you other guys.
Even if you want to be an infernal warlock primary. Star Pact is too good to give up if you can get it as a feat. You aren't likely to use all of your temp hit points between any given enemy going down so instead you pick up +2 to attack or more(if multiple enemies go down, you can pick up the temp hit points and then +2 to attack from all the rest!).
Add in the fact that you get an extra at will AND you get to use the bonus abilities of powers from both pact, and its just ridiculous.