I used DB 1-83 5 toons and 1-80 on 5 toons just recently.
My recommendation:
This group gives +10% attack power,+5% crit,+5% stats,-12% armor on bosses,+10% stamina,+10% spell power.
Tank: Pally or warrior, both do very nice dps.
DPS: Feral Druid or Monk
DPS: Hunter
DPS: Warlock
Healer: I've only tried monk n priest very little, both worked well tho. Druid healer does need alittle class config especially at the lower levels, but once they're configured correctly they never let me die, and if it happens due to a too big pull, instant combat ress.
Edit: DEFINITELY go warrior tank for the higher dps and priest healer for the speedbuff.
Only team I haven't tested out yet that crossed my mind was
Warrior tank
Feraldruid,hunter,rogue
Priset healer
Would def be some fighting between the rogue and the druid, but would add an 10% ranged and melee haste to the full physical dps team.
I used singular for everything, don't roll shammy as they really suck for dps 1-60, Hunter seems to always be in the top 2, and lock rly gets high with better gear.
For my next group I will be doing with full looms once my 83s are 90 and moved to another acc.
I did 90% of the tanking myself, there are alot of instances that the bots fail at if left unattended to tank. However I'll be mapping out the instances that it can afk at least for me, so I'll just be able to queue for specifics while afk.
Currently:
DeadminesStockades
Scarlet Halls
Scarlet Monestary (not recommended with weak gear as the boss encounter gets hard for the healer)
Uldaman
RFK
Ramparts
Slave Pens
MGT
UTK