I don't think it's toxic. Using momentum shift like this adds an element of strategy for both you and your opponent. Plus it's not exactly free either. To do this you have to use timeouts or give your opponent five yards which might end up being the reason you lose.
Honestly, it even seems kinda bad in matchups where you're opponent isn't using Dickerson/Bo or any of the other players with combine xfactors. The aka/charge up xfactors activate often enough that you really have to be strategic with when you bring in momentum shift.