| I don't think it's overpowered in the "will this break my game" sense.
I do think it is overpowered in the "every Warlock will take this feat" sense. On the other hand, part of the point of the Dragon article seemed to be about fixing the fact that "core" Star Pact Warlocks get kinda screwed. But fixing that through feats means everyone will take those feats.
I've considered houseruling it to 4+level damage or something, just to restrain the low-level awesomeness to where one might have at least a brief second thought about using it. | 
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