5 class mix going on.. this is what i think..

Shaman (you need the totems)
Druid (gives you the increased crit and all that.. maybe some quick heals.. mana regen
Paladin I would go with because of the high survivablilty as a tank
Mage (increase intelllect.. slow things down. and food and water.. you would waste soooo much money making water for 5 guys 1-80 doing instances
Shaman again.. (i think the increased shaman for more totems.. most of the stack, and the double chain heal helps alot.. ) also switching on and off reincarnation with 2 guys helps :0..
(to replace the shaman).. make the druid and shaman dps ele.. and have a priest heal.. This helps because priests have a ton of buffs. especially the mana regen. and the shields, and increased stam