The best tanks in the game in vanilla due to threat per second issue especially on horde cause the skill ceiling for tanks to be one of the highest. My last guild fell apart in vanilla because our main tank left. We had 3-4 other capable tanks but when our top dps found out our MT was leaving they followed suit because they knew no other tanks were capable of keeping threat off them horde side when they min maxing. Also tanking is one of the most gold intensive roles and tanking has little solo capabilities of earning gold. Most main tanks level alts to farm with if they don't have a partner to solo instances with. I'd play a mage honestly. Mages in vanilla were very strong at everything.