Good 5 man comps purely for pve / dungeon leveling

[Tazeon]

The above responses are really good. I would not recommend a melee team for your first team.

If you are only having one single group to cap I would do:

Tank+2Mages+Warlock+Healer

I fully agree with this suggestion:
No melee team as a new multiboxer.

tank + healer + 3 casters (2x mages + 1 wl or 3 mages)
have the most advantages

tank:
paladin - if you play alliance for easier aoe tanking and if want to play tbc
warrior - you can get very good tankgear in ZG or if you want to raid as a tank or dd in mc + bwl
druid - a little better aoe threat then warrior, but not as good as a paladin, motw,

healer:
shaman - if you play horde and your main farm is DME, improved chance to get a raidspot for shaman healer or if you want to play tbc
priest - sta buff and shield for casters, you can buy bis healing staff from another mc raid
paladin - if you play alliance and no paladin tank, kings or aggro reduce for caster
druid - not recommended because you have no ressurection (or you play with paladin tank)

caster:
2x mages + 1 wl - have more utility (port, soulstone, healthstone, + sta buff, fire shield or aoe tank if you play SL)
3x mages - more aoe and single target damage (especially if you play fire mages)