Why not 4 locks and a shadow priest? good synergy, you can keep soulstone up on the priest, and rez when needed. You could use your existing lock to boost the other 4 and speed up the process. A shammy would be good, with flametongue totem or totem of wrath. you could also go with a healer, tank and 3 dps. or you could just boost 4 dps with your pally.