First off, no, it's not just you. This is one of the MOST powerful spells in the entire game, in my not-so-humble opinion. It certainly goes a long way toward evening the sorc w/ wizard, though, eh?
It blocks line of effect, so I don't see how an ability being Su should matter. Certainly not Sp, which for the most part interact with things the same way spells do.
As for what to do with it, I don't know. Could ban it. My group has fond memories of using it to utterly screw over the bad guys, so I didn't want to scrap it. I altered it to give a chance of blocking line of sight/effect, I think it's still quite strong. Here is my houserule:
"Wings of Cover grants a +8 cover bonus to AC and +4 cover bonus to reflex saves against one attack. Any targeted or area attack/spell/ability that does not need to hit AC or give a reflex save instead has a 50% chance of being stopped by the wings blocking line of sight and effect. Any ability that does not require line of sight/effect to function is unaffected by the use of this spell."
Note the text follows order of application. A touch spell would not be subject to the 50% chance, but instead the cover AC. A purely targeted spell would. I'm not even going to pretend this makes perfect sense within the rules in how it functions, but at least it's more balanced.