Tough call but I think Treachery could be the better option, as you get a host of good effects from Fade. 30%DR from Shaftstop in NM is overkill I’d say.
I’d thought only on-weapon IAS affects Fury regardless of weapon used, but if off-weapon IAS does affect slower ones, even better.
And as others have said, can always toss the Treach on your merc when you find an upgrade.
Duriel’s Shell could be a good one if Meph drops it for you. +Strength & life, resists, not to mention CBF.
Good luck
