I'll have to side with Eteocles on this one.
personally i have the option to have my lvl 65 warrior tank and powerlvl my clones, but i'm sticking with my lower lvl pally.. it's worth getting used to it.. however lvl 20-60 tanking pally tanking doesn't change too much so you could get him up to that lvl and then use him as your tank. The advantage of having ur pally at lvl 70 will be that you can powerlevel any team up to 70 very quickly providing you stick to the trinity rule..tank+healing+dps
there are a few ways of sorting out ur team 1 tank + 4hybrids.. or 1 tank + healer + dps

option 1:

4 caster hybrids of the same kind.. druids, shamans, Preists.. not paladins as these are melee.. (priests included as they can dps and heal)

Reasons for taking these:
-stacking spells means you don't have to worry about one class casting at a different rate = less micromanagement
-insane dps.. dps using hybrid classes stacked like this (especially shamans) can often outweigh problems with lack of CC

cons per class:
Druid.. if boomkin speced, no stacking aura and can't heal whilst in that form.. limited CC
Priest.. very very squishy
Shaman.. lack of CC

Pros:
Druid.. some AoE, high burst
Priest.. great healing and utility
Shamans.. totem defence stacking, high burst, and high armour value

option 2:

4 casters.. 1 healer + 3 dpsers

very stable setup.. high dps and good potential CC

Healer:

Pally: buffs, good healing (single target only!)
Priest: arguably the best group healer, buffs and some CC.. (undead shackling ftw)
Shaman: totem micromanagement for one character could become a little annoying but provide good buffs nonetheless.. good group healing, wipe insurance
druid: meh buffs.. great healing efficiency with hots, but may require constant application of said hots (hard enough being a healer as it is :P)

Dps:

Mage: arguably the best choice.. 3 sheeps, frost nova, AoE, great burst, panic button (Ice Block)
Warlock: great dps, less CC then a mage tho (unless you use succubus wisely)
Hybrids as before



Personally I'll be using 4 shamans simply cos i love the class and always have