From my understanding Dancer's DPS is severely effected by the 1 second before and 1 second after you use a job ability it suspends your auto attacks. Additionally you don't have the ability to use SATA to combine with weapon skills tho you can self chain and use flourishes. Their damage output is just lower than thf and unless SE fixes the job ability delay issues they're always going to be a mediocre DD that doesn't offer any unique support abilities that someone else can't do better.
They are a god of soloing but even then, their damage output is low. They are one of the best to farm dynamis with for example, but they are 3rd place simply because they can't kill as fast as Beastmaster and Thief. Again this is just my understanding from what I've read. Byrth in the dancer forum would be the best to ask. If he can get the devs to listen to him about the JA delay I see Dancer becoming a competitive pick to every event. Having things like Enfire stack with Drain samba wouldn't hurt either.
I don't know that Byrth will get his wish though because I don't think it's an easy thing to fix... it's probably a relic of some sort of programming aimed at making sure it runs on ps2, xbox and PC, it could even just be a way to ensure all animations have time to finish playing after you use a job ability and to make that one change... they'd have to reprogram every job ability in the game. So I don't know but it's a big problem, I hate to even use steps when subjobbing dancer it really kills your damage output.
Actually steps is a critical part of dancer dps. Presto steps then steps. Climatic flourish rudra storm at 1750tp. More steps rudra storm reverse flourish rudra storm skillchain repeat.
I been winning the parses as dancer in a few things. Except voidwatch when I am dual boxing and end up in second.
I also did a 88k skillchain on largantua at 1750 tp.