Thank you for your input guys!

I agree that the perma-mezzing of Provoke and 5s grace period is broken. Only build I'd be able to do that in is yellow/blue, and I don't think I've ever actually used that build. I only have that build "just in case", but that case hasn't come yet.

I'll keep the Gamble Chance on my Red/Blue Burglar tools, since I don't really find myself lacking other legacies on it. I like dwarfThar's idea to use it for bypassing avoidances in Mordor. On my Support tools, I'll replace it with Positional Damage or Critical Multiplier. (My support book isn't very DPS-oriented.)