Waller - if placed directly at you, which they usually do, your shots won't hit and needs to re-position.... but can't without Vault and sometimes, even with Vault, you can't.
Nightmarish and Knockback- combo'ed with any affix like Molten, Electrified, Plague, Firechains pretty much cancels your Channeling and positioning.
Frozen- annoying to an extent but can be DODGED and can be bypassed via Smokescreen.. so it's not that much of a problem until they spam it like there's no tomorrow.
So far.. how'd you guys deal with that?
Vault to reposition.
Smokescreen to.. both reposition and avoid certain deadly situations
Re-channeling RF and popping Shadow Power takes it toll when 3 elites keeps on Vortexing you and stuff. LOL
Share your ideas people ;)