I think BLM's fire/ice, BRD's dots (though they could be turned into a single dot tbh and it would be fine), SAM's dot, and healer dots are good tension and management. I actually would like BLM's thunder to be removed or turned into an ogcd, because it's in a terrible spot of the damage being basically pointless and it's a newb trap. Warrior's and DRK's are both enjoyable to me, but neither is particularly interesting; Warrior's just means your combo is 1 2 3 1 2 4 1 2 3, while DRK's is a check that you're using your MP regularly.

In general, to me, a dot should not just be a timer you have to maintain; it should either be part of a decision tree (like samurai's) or a way to keep up your damage even if something happens to your uptime (healer). Buff timers also should be in a spot where it isn't excruciating if something goes wrong but it's rewarding to manage them successfully; this is to me a lot of why EW BLM was a great class and at the root of many objections to DT BLM, that your ways to work around the BLM timers were nerfed so you more often just failed with nothing you can do about it.

I don't think Warrior's or Reaper's really do anything besides exist, but nor are they pain points while playing, so I'm pretty neutral on them. The ninja main I know was perfectly happy with the removal of the buff in DT because it also just existed rather than being something you have to play around.

I really wish they made it easy to tell how much damage a dot does, because my biggest problem with them is that the Actions & Traits menu doesn't make it clear how much damage they do overall, and I don't know offhand how they interact with my stats.

I think BLU's dot gameplay is substantially in response to the hot mess that is Moon Flute, which is a strong contender for worst designed skill in the game. The dots and Apokalypsis do a good job of making it feel satisfying to have correctly executed your Moon Flute window, but regardless spending 15 seconds unable to cast is profoundly unsatisfying. I like the feeling of dots taking out my enemies on BLU, but unfortunately the dot mage stuff makes it even less likely they'll ever do a Moon Flute rework.