I noticed this in alot of the beta videos I have seen too but hadn't seen a video lay it out so clearly.
Basically, if you see the hit animation of a monster, you get hit everytime.
It was reported on the forums and Vasadan replied, but never exactly said "noted, it will be fixed" or anything like that.
Isn't playing mele hard enough with out getting hit by EVERY animation? I think, logically, this MUST be a beta issue and will be fixed. My worry is that due to the online nature of D3, this was deemed acceptable. I don't think it is honestly.