I don't even pay attention to regens and medicas and stuff when I'm pulling multiple mobs. I just tamahawk or flash everything as I'm running along gathering because it's a good idea. If for whatever reason the mobs fall off me on the way to stopping my path of gathering, I'll stop and run back to grab them all up and cut my gathering short.

As a tank, if my tama or a flash doesn't hold a mob well enough from a tick or two of regen, I'll feel like a failure of a tank.

People have different playstyles. If as a tank you can't deal with people playing differently (like using regens), learn to deal with it. Getting pissy about people not playing exactly the way you want them to not only makes you look like a jerk, but you'll also have a lot less fun.