His super cost is just fine. It's his AP gain that is the issue here.
Super costs for Kratos
Level 1 = 150 AP Level 2 = 400 AP Level 3 = 750 AP
His super cost is actually about high as it gets. Most character's level 3s are 750 AP, with the exception being cinematic level 3s (Parappa, Heihachi, Spike, and Toro) for 600 AP, and Good Cole's, Sly's, and Sir Dan's level 3 for 675 AP. Everyone else has a level 1 that ranges from 100-150 AP, a level 2 from 320-400 AP, and a level 3 at 750 AP. Most seem to have the 150-400-750 spread.