People are making good points on all parts of the spectrum.
I have always preferred playing a dps, when SE announced DRK I re-subbed to the game for DRK is my favorite class and looked forward to using it once again. Finding out that it would a tank role was not what I wanted to hear but since it was my favorite I would still play it. I don't mind being a tank role, still would prefer DRK to be dps but it is what it is.
The biggest let down about DRK is that there is the lack of sacrifice hp skills or other skills that are iconic to DRK from the rest of the FF series. SE could of made it work and still be a tank role.

So for Samurai whether its tank or dps as long as SE executes it properly is what should matter most.

I do agree that there should be a dps class that uses swords. Samurai being introduced as dps would definitely steal people from tank roles. I myself prefer a sword dps class so thinking forward what will hold my attention, my favorite class; DRK or sword dps class; potentially samurai.

Personally I think SE should bring Samurai into the game as tank and convert DRK to dps. hahahhaha never will happen...or will it.....