Nah. Backstab stinks. Too easy for enemies and players both to get behind others. I mean, I get that if you are defending against more than 1 person in melee it is harder, so I could see getting advantage if facing more than 1 at a time, but not just running around behind someone.
If they put backstab back, they would need to make it only if you have 2 allies facing a single foe. Then, at least, you are limiting it to flanking and providing more strategy for melee fighters.