my money is on the clerics. A persistent/extend buffing session makes it so they are nigh invulnerable. By 16th level they dang well better have armor of fortificaiton, so the rogues sneak attacks are now moot. Then add in attack spells and it just be ugly. If the rogue and fighter have insane epic SR items it might go poorly for the clerics, otherwise the clerics should jsut grinf the rogue and fighter up.
Good tactics are already mentioned above, but add in harm, with a quickened cause modeate wounds for an up close fighter. Or heck harm at range is only an 8th level spell with the right metamagic feat.
Check the cleric save or die list, destruction does 10d6 on a save and is a fort save, two of those at the rogue and the rogue is likely by-by.
Metagame, and rightfully so. Read up on augry, divinaiton, and the host of other God is on my speed dial spells. Every cleric I know casts those spells as a routine in the morning to help prepare for the day.
If i had my books I'd give you tons more ideas, but I'm drawing a blank now.