Yeah, that is pretty good... my thinking was that, as it's so darn limited (basically to one spell and its permutations) it should be pretty darn good. To get the greater version, you need to invest three feats (including SF Abjuration), none of which are good for much else.
Keep in mind, too, that with a standard dispel, you still max out at +18 (since the base bonus maxes out at +10 and you have two +4s on top of it).
Again, with the prerequisites in mind, is this too powerful? I tentatively think it's okay, having given a lot of thought to it... but maybe you're right, maybe it is too much. Still, I really think +2/+2 is too little for such a restricted feat; but as these feats are still in development, my mind is far from made up.