I don't have many issues with the current design of the DPS role. However, I can admit that my time playing DPS is restricted to mainly the melee sub role, of which I play three (SAM, NIN, MNK). I do have some experience playing DNC as well, but my desire to play DNC is purely aesthetic. If I play it well, it's because it is a very straight forward job.
I have not tanked anything really respectable other than Sephirot Unreal. My issues with tanks comes strictly from my experience with having to heal them. My experience here has that well over 50% of the tanks I group with do not use, or do not know how to use their mitigation properly. As such, I do have to heal them to keep them from dying. However, when I get a good tank, they are virtually unkillable so it is basically from one end of an extreme to the other. In the thread I started about suggesting a super TB, or mini enrage, the intention of this thread was to point out the issues with their self-sustain. This came from an EX encounter with Rubicante where neither the boss, or the tank could kill the other, and the group was forced to watch this tank solo the boss for over five minutes until he finally enraged.
I typically don't like talking about healer issues anymore because my views tend to spark a lot of controversy. That in itself is fine, but it becomes a back and forth crapfest with each side trying to shove their views into the other's brain, and not even attempting to hear the other side out, which ends up leading to personal attacks, and other forms of non-civil trading of words. What I will say is that I think some tank and healer issues are related and coincide with each other. While both roles also have their respective issues as a result of the way encounters are designed.
It will be interesting to see what SE does in 7.0, assuming they do anything at all. Even though I defend these guys quite a bit, there are undoubtedly issues across all three roles that are causing grievances among the playerbase. Even I can admit that these need to be addressed if they care about the game and the playerbase.