Samuai DPS
Red Mage tank
Dancer healer

I'm not sure why people still think that having another tank class is going to fix the shortage of tanks. People don't tank because it's the most demanding role (except maybe healers) and requires the most attention while playing. People get nervous queuing with them. SE could add 3 more tank classes and no dps/healer classes and it still wouldn't change the shortage issue.