For PvE, I'd go with:
- 1x Prot Paladin
- 3x Elem. Shaman
- 1x Demo/Destro Warlock.

Possibly dual-spec one of the shammies to Resto.
That would make harder content (ie, being undergeared) a lot easier.

If you want to do everything at 60th, you could turn off experience most of the way in 60.
And do as much Classic Warcraft stuff as you'd like.

Then turn experience back on, level to 70th.
And do the same, as you go through all the level 70 content.