Byakko's have no place ever, if you don't have ogier's/shelled out for Avant+1 use Emp+2 legs at the very least. Acc should be capped so heafoc/augmented Hec hands beat Rav+2.
Zahak's might be better for fodder/Visions NMs but grim should win otherwise, unless you got Rheic/Phorcys body.
@above: no, GH is bad and you should feel bad for defending it. doing 741 means buffs were down you missed first hit only 1 extra hit landed and it didn't crit. If you are seeing it for other reasons the problem is with your gear and atma choices not UF's crit rate.