It's not about being difficult to gain aggro. That's not a problem. The issue is, if you have Regen on the tank before they pull, only the mob that the tank initially hits will move towards him. The links will move towards you.

Normally I don't find it a problem... just a slight annoyance. I generally position myself so that I'd be able to pick them up easily even if they go after the healer. But it is annoying. When we are able to pull properly, the mobs come straight for us and it's easy to round them up. If they end up running in different directions, it can be a pain.

I would never initiate a vote-kick on a healer applying regen before the fight. Though I might ask the healer to stop.