Sackboy is fine it's just people keep seeming to ignore him in a match then act all surprised when he's managed to work up a level 3 :L
Just because you find those characters as a problem doesn't mean they r OP. You just need to get better. They should set it up so you play ppl your own level though. I rarely play any other black belts. Kratos and sackboys AP gain are fine. Only reason they raise so fast is because you guys get into nice little clumps so they can hit you all at the same time and you triple there AP per atk. That's not cheap, you just need to strategize and stop hitting square hoping someone gets hit.
It's impossible to balance each character to perfection. Since I've seen EVERY single character listed as over and underpowered, I'd say it's pretty close to being balanced. Sackboy takes skill to play as, you can't have your little brother pick up the controller and destroy people online. Kratos doesn't take skill, but even if you are skillful, you can't do much with him. I've never met a Kratos online that I couldn't beat.
Patches the Hyena (Dark/Demon's Souls) for All-Stars! His level three could have the player leave the match, enter a random match, and get one-hit-one-kill's on everybody! xD
. Kratos must have his chain grab nerfed to the point where it can't be spammed and have his AP gain cut by like 30-40%. Every Kratos I play gets to at least their level 2 no matter what. Raiden needs a range nerf on his supers (1,2). He possibly might need another type of nerf on his combos, I'm not sure. Sly is both annoying and OP. His moves are fine. Its his supers and defensive moves that are irritating. His level 1 has the most ridiculous range ever. Even when your not near it, it'll hit. I cannot begin to name how many multi-kills I get effortlessly, just from using that super. His invisibility is pretty OP. Play Nathan Drake's rival fight on AS or FP's arcade on All Star. It truly proves how annoying Sly gets when used efficiently. I suggest making it so Sly becomes invincible in this state, but you can see his player arrow. If I remember correctly, the moment Sly attacks he loses his invisibility so that would work out decently. Ratchet's level 3 needs a buff as in a slight radius increase. People might actually not spam Ratchet's level 1 if it gets fixed. Jak just needs a buff. I've seen 1 Jak online. Some say hes fine, but I don't think so. Sackboy is just annoying. The bubbles for his L3 need to be able to actually evade Sackboy. He gets an easy 6 kills with that super most of the time.