Let's talk about regen :)

[crystalfire808]

Regen will draw aggro to the healer on the first tick after pull. Tanks should cancel regens when going to pull, and mages should avoid casting regen toward the end of a pull.

In general, regen is wonderful considering the instant cast. It's good for throwing on dps party members and great for countering DoTs (like the evil, terrible, annoying AV poison). However, it does cost a bit of MP to cast, so it should only be used when it will be used to its full potential (all ticks healing without health being maxed out).

I typically use the stoneskin+regen tactic in most normal circumstances at the beginning of a pull. It gives a buffer to throw up some DoTs on the mobs if you so choose, or you can stand around waiting for your mp to refill.

EDIT: Another situation where regen is very helpful is in fights where you have to be moving constantly, therefore making casting difficult, such as the ogre boss in Dzemael Darkhold. Regen saves lives!