Sly's supers are not OP'd. Maybe his level 1 is hard to dodge or interrupt, but it's also comparatively hard for Sly to build up to a level 1 compared to others like dante, raiden, kratos, etc...
Same goes for his level 3, Kratos can get to a level 3 much quicker than Sly can.
In my opinion anyway.
Quickness to a level 3 is dependent on the player, just sayin. And I just want to compare to other fighting games. They allow unbreakable combos in games like Tekken tag ect. Also you can combo into ultimates to unleash maximum damage on the opponent. Taking that out would drastically change the game, just like if they tampered with comboing into level one it would make "Playstation All-Stars Battle Royale" no longer the same game. That is how big of a change they would have to make.
it's also comparatively hard for Sly to build up to a level 1 compared to others like dante, raiden, kratos, etc...
Maybe when compared to those guys (I think Dante actually has a harder time than Sly), but Sly can rack up AP fairly quickly. Especially in the hands of a good player.
His ability to steal AP, as well as his counter that puts him immediately behind someone so he can steal the AP don't really make it that hard for him.