MrSinister Needs Tuning

Most of the players agree that MrSinister can be a pain to fight against. But from being a pain to being an extremely op defender is far. Just a screenshot from arena against him with about same challenge rating champ says it all:

Needed about 80 hits to finally bring him down. How balanced is that?

Needed about 80 hits to finally bring him down. How balanced is that?
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Comments
Use a heal block against him and watch him melt.
Hint: SP3 doesn't crit. Some fights require you understand the game mechanics more than others, and this is one of those.