Nightbane

[Professor Frink]

8) Having a unitframes mod that allows you to quickly and easily see who Aran is targetting and what Aran is casting at any moment really helps in the healing department. You want those heals landing as the spell is landing, not 3-4 seconds afterward, else you get behind in the healing and it's hard to catch up.
-Bolty

I use FocusFrame for this, it gives you a draggable focus box that looks just like the standard UI target box, complete with target of focus, cast bar, debuffs, lucky charm, etc. Set a keybind for "focus target" and focus aran before the fight to keep an eye on him while keeping your target slot free for healing.

Also handy for crowd control like Lissa above mentioned; I prefer to adjust my focus manually (w/ focus target & target focus keys) so i just have a

/cast [target=focus,harm,nodead,exists] Shackle Undead
/cast Shackle Undead

macro to shackle my focus, or shackle my target if my focus is invalid.

-- frink