Dynamis has become a housing center and a venue server. It's pretty active for that for sure. I have 4 characters on Dynamis all 100 end game and I do my content on Aether or Crystal. It's what people got into the habit of doing there. I don't see it changing unless they lock out DC travel.

On another note Materia is worse than Dynamis yet people on that DC are prisoners and can't go anywhere to get content done. Pretty sad given they pay the same sub fee.