If these were people that you knew you would start playing with from the beginning, why did you not plan this a little better? Hey bob, what are you playing? Oh, I wanna be a PLD, ok cool, and Bill? He is going WAR. Well, I guess since we only need two tanks I will roll a DRG. Ok cool! For a group of people you play together with frequently, sounds like you don't do a lot of... you know... communicating...

Not trying to be mean, but I am not sure where you ever thought you would need more than 2 tanks, when most content is 1 tank-able. This just seems silly to me.

Regarding your, 300 myth tome cap preventing you from playing another class, I feel I should point out, that you only need DL to clear up through turn 4, and DL works on more than one class... generally speaking (the physical dps are the exception to this it seems) and even at that, you can still farm those up rather quickly if you wanted to switch roles. Is it boring as hell? Yes... but doable. Better to switch now, before you spend your myth tomes... just saying...