WRT Havok I'm pretty sure a macro like this would solve most of the issues people are having
/cast [@focustarget, harm][@focus] Havok
On a fight where the target you want to cast Havok on changes frequently you'd have the tank that picks those mobs up as your focus (or some other dps that is physically swapping targets each time), on fight where it's just a single mob you just set it as your focus.