I like the idea of the perk. But I think its way to weak. Iron Grasp reduces the "wiggle strength" by 25/50/75% and boil over increases the wiggle strength by the same value.
But iron grasp also contains that you need more time to wiggle out. What about adding sth like this to Boil over:
You need less time to wiggle free from the killer by the same value iron grasp has. It would be perfectly balanced then, because you can counter the perk with iron grasp.
What do you guys think?