So the wizard is beset by the kraken. Rather than submit to the grapple, he twists out of the way (wrenching his back), falls, and rolls. If he tries to cast a spell on his next action, he has to make a Concentration check (or whatever). He takes damage from the tentacle, as if he had been hit, but is not grappled. Sure, the kraken can follow that up and continue to attack, but that's taking his actions. That's a lot better than taking his -20 on one tentacle to completely nullify the wizard. Sure, the wizard will spend some fights avoiding grapples, but now it's useful and heroic.