I miss prenerf Resonating Mawfang or whatever. Having our interrupt do 10% of the targets health was hilarious. Broken of course, but hilarious nonetheless.
Honestly, as Vengeance, the powers to make Fel Dev not incur a cd are nice if you can get enough of those, along with the immunity during Fel Dev. But past that, the uh…forget its name but it makes Infernal Strike do 400% more damage, that one is pretty nice. And downright hilarious if you can pair it with the 100% increased ranged and the no cd power that lasts for 2 minutes.
Edit:
The power that makes Imprison charm the target. That can also be insanely OP if you grab some the nastier casters. Is useless on the final boss level but can help a lot prior.