How much damage would I lose changing one of my 3 dps mages to a dps priest? 4 out of 5 chars of the comp I want to run I have pretty much decided already. Losing the 3rd arcane explosion and replacing it with holy nova would be a dps loss for sure, but how noticible would it be?

This is a Wpvp and dungeon farming group

1 pally(main)
1 warrior
2 mages
1 mage or priest

The reasons why I would like a dps priest are that I can switch comps around if I get bored, and I can make the priest a night elf along with the warrior.

So my choice now is between:
Team 1
1 human paladin (heal)
1 human warrior (tank)
3 human mages (dps)

Or Team 2 and 2.5

Team 2
1 human paladin (heals)
1 Nelf warrior (tank)
2 human mages (dps)
1 Nelf priest (dps)

Team 2.5 (team 2's 2nd composition)
1 human paladin (Tank)
1 Nelf priest (heals)
2 human mages (dps)
1 Nelf warrior (dps)