I play PLD, BRD, and NIN. Paladin used to be my main, but I've since made it ninja. I can say that throughout leveling in dungeons, and especially now in expert roulettes, it is quite easy for a ninja, with the right rotation, to scale up the enmity pretty quickly, especially after Trick Attack and a critical Raiton. When I get in dungeons with tanks in or around i100, I usually always hold back on my rotation (ninja is i113 atm).

I think the core principle that many forget is that success in the dungeon is a team effort, and part of the dps responsibility is watching their aggro and, if need be, switching to a target that has not been engaged yet by you (that the tank already has built enmity on). Rotating trash mobs is as easily done as it is as a tank, there's no reason for a dps to take aggro unless they just don't know about the bars, or do it on purpose.

On bard and ninja both, in low level dungeons, taking hate is even easier, and so it is even more of responsibility to use all the tools SE has given to make the run go as smoothly as possible, including disengaging one mob to change to another when aggro level is too high.