Initial enmity generation and player bad habits.

[Duelle]

I am having to say something like "please don't use regen during a pull"

I'm still coming to terms with why the devs would make overhealing from HoTs generate aggro. Regen (or should I say, Prayer of Mending) prior to pull is a habit healers from WoW developed to cushion damage taken by the tank during the pull while the tank positions the boss and so on. That tactic may not seem valid or useful here with stoneskin and adloquium, but a WAR tank would benefit from having that extra cushion of healing, for example.