A timeout is a loss for the attacker. That means that once you get a top spot and put him in your defense, no one will ever be able to beat you.
Not if every white triggers his shield. Even heroes who don't rely on their whites still have whites, and while his shield is active, you can't even do basic attacks.
That's the skill description from the code. So it looks like he's not behaving as intended. His shield lasts for a very long time (15 seconds by my count), and seems to always activate when his HP is very low. I haven't been able to kill him in one hit to get around the shield (similar to how you can't kill KK with magic damage, no matter how much damage you do in one shot).
This means that I was wrong about enemy whites activating his skill. The real thing he blocks is not white skills, but screen freeze. This is similar to Plant Soul. Once her white activates, it will stay active for the rest of the fight if she's frozen by, for example, a bard+moon combination. The difference is that Snapper Bone's skill is guaranteed to activate, so he'll always beat screen-freeze teams.
The problem is, the only hope of beating certain teams is screen freeze, which means that Snapper is just going to become yet another must-have hero for every team. And in FP and Col, that means a defense team that combines screen freeze and snapper will always win. Either the attacker won't have screen freeze and will lose, or the attacker will have it, and will time out. The only way to beat snapper is true damage, and the heroes that have that might not fit into teams that can beat KK.
So without fixing either KK or screen freeze first, I believe that Snapper Bone will break the game.