I can do all the dungeons in classic. I've done UBRS clears with a buddy who plays prot paladin / 3x mage / holy paladin.

My comp is a warrior / 2x mage / hunter / priest. A 3rd mage would have been better but I raid weekly on my warrior and hunter which were my intentions going into classic. I will say that having the hunter with jumper cables can save some running back because a warrior / 3x mage / priest has no wipe protection.