Skills going off but not registering?

I was in Coerthas on Saturday night and I noticed that sometimes my skills would either:

A. Go off, full animation, and the skill wouldn't register (no damage, nothing in chat log, combo'd skills don't light up).

B. Animation starts halfway, then cancels itself (GCD is immediately refunded).

Really obnoxious and hard to get aggro when your first 3 Fast Blades don't actually go off. Anyone else experiencing this as of recently? It's been happening all the time ever since.