I think DRK have a bigger potential to be a tank coz its similar to WAR; they both 2h, they rely on sacrificing hp/str for gain/loss, both rely on highest HP/dodge/parry ability than PLD. I think SE will make DRK as tank and SAM as the first 2h dps/DD class. Ninja will probably fall as a support/DOT DD class like SMN. They probably won't put Utsusemi on ninja, seeing it was abused in FFXI.