As a WHM there are some fights where I'll put Regen on everyone during it, but that is VERY rare. I know when to use it and when not to so that doesn't happen to often.

Other than that I only ever put Regen on the tank after they have established hate. Then I keep it active on them. If Regen is still active after the fight and we engage more mobs I make sure that I am right next to the tank. I've seen when tanks have Regen on them before a fight that mobs will come at me so standing next to my tank helps him a ton with pulling establishing enmity on any mob instead of running around to catch the ones on me. Then I can move back a bit.

I love Regen and used properly I can put out more dps which only helps the team by being able to help kill mobs faster. For the WHM's who don't DPS during dungeons you should be ashamed.. We can put out a TON of DPS! Just remember that we are healers first and DPS second and all is well..