This issue is probably as a side effect of the damage assignment rules change, but while there no longer is priority between damage assignment and dealing, there still IS supposed to be priority between each step of combat, like declaring blockers step and damage steps.

I just lost a game with exact damage, I had Ygra on the field (all other creatures are also food) and a Cauldron Familiar in the graveyard (I can sacrifice food to reanimate the creature) I blocked with all of my creatures and intended to sacrifice one of the blocking creatures to return Cauldron Familiar to the battlefield, gaining me one life and keeping me alive. However as soon as I declared blockers, the game moved to damage preventing me from bringing back my Familiar and surviving the turn to combo off and win on my next turn.