I can't find the forum post where I originally read it, but someone had discovered that since the game's full release Enrage only gives you 100% crit chance on abilities on your second turn. The same turn as you cast it it only works for basic attacks.
I have no idea whether that's intended or not though, it seems really weird considering the skill tooltip doesn't say anything about it.
It doesn't even do that, at least not for me. Both on the first and 2nd turn the only thing that crits reliably are the normal attacks.