Just my 2 cents

I use unchained in the pull if I have full stacks going in. And some people may not agree with me but I'll start off with infuriate to give myself 5 stacks on the pull. It just makes it easier to establish threat that way. May not be at all necessary but I have near zero issues with initial aggro unless I get that dumb ass dps who wants to balls to the wall the boss before I even hot the thing with a tomahawk.

Other than that, I will use unchained only during a burn phase... Assuming I'm even in defiance at that point. At higher levels I'm either in deliverance post 52 or out of defiance below 52 after I have my threat established. Unless the healer needs me to be in defiance.