The only downside of repeater regions when using modifier keys is that you are temporarily stopping your DPS when pressing ctrl (or any modifier) -> left mouse button before resuming. Well I am in any case.

Especially in intensive healing fights and with a tree, I'm regularly playing twister with the keyboard with shift LMB for rejuv, ctrl LMB for regrowth etc... I think i may go to using repeater regions for light healing only and cleansing and macro heavy healing to numpad.