I loved shadow priest at the time. You had a very methodical/cyclical rotation, you are ranged and you could defensively dispel so you had incentive to show raidframes.
Elemental shaman worked really well too for the offensive aspect, but I lost track of the defensive stuff. I blame it on the spammy playstyle.
I hate resto druid. I can make it work in CMs because of the CM healing playstyle, but for raiding the UI-centric maintenance'y playstyle of resto druid is horrible for me. My performance drops like crazy when I wanna do anything besides mechanics and healing.
I think the more binary and easy a class is, plus ranged, the better. I can see holy paladin work really well.
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Very good suggestion! Have a tank call all the tank-relevant stuff and have someone else call everything else. Works really well whenever I run into a tank that is competent enough to do it, and is fun to lead with.