On xbox, off balance is nor correctly applying to overland mobs in Vvardenfell (have not tested other zones). Here is what works and what doesn’t as observed so far:
1) Vampire passive savage feeding does not set mobs off balance (it also doesn’t stun them).
2) Blocking a heavy attack from a mob does not set mobs off balance.
3) DK burning talons will properly set mobs off balance with whip (flame lash)
The impact of this is pretty significant. Heavy attacks will not knock down mobs or do extra damage. Whip works on far fewer things.