Never seen someone bitching if tank was at least half-decent. New or not. On the other hand bitchy tanks with "omgloldpsimouttahere" attitude for no reason are quite common. Failed once at Demon Wall? DFed into WP without relic and can't speedrun? "Bye n00bs i will get another DPS in no time". Don't open that can of worms.

Low-level roulette won't help you get those mounts.
It will. To tank in 8-man dungeons, one has to level tank up to 50 first - and DR still the best time/exp method to level alt classes.
So, i've got 50 PLD, but want a bear? Time to blow the dust from that newb MRD!