To me, the combo backswing with a two-hander can be a downright annoying and game-breaking combo. It allows you to strike an opponent with a very heavy and powerful weapon and immediately overcome inertia to hurl the weapon in an opposite direction. The backswing part of the combo makes this attack much, much faster than two sequential horizontal strikes.
I suggest either removing the backswing from 2h weapons, or simply halve the damage the swing deals. If half is too much, maybe a 35% decrease?