does units heal after rampage resolves

No — Rampage doesn't trigger any healing when it resolves.

Rampage is a spell that makes the two units deal damage to each other. That's spell damage, not a Combat Showdown, so no Combat Cleanup happens and nothing heals (Rule 143.3.b). Any damage dealt stays marked until either the next combat showdown ends (global heal) or the end of the turn, whichever comes first.