As someone who considers himself a Blu first and foremost, I would definitely say not to consider it as your "primary job" before you've got another more universally desired job decently geared for endgame.
Bluemage can participate in at least passably in any endgame content (But then again, so can any melee if well geared and well played), that said, it's not really desired by the community except in two endgame events that I can think of, Bee and Shark lowman delve.
In Ceizak, Absolute Terror is wonderful for the Transcendant Scorpion @50%, and Requiescat is nice for the Gnat and Bee.
In Foret, Absolute Terror is nice on Neverrik, though with a decent stunner, this is not as attractive as it once was, it's still a plus. And Requiescat is still somewhat nice on Krabakarpo when he's got his PDT up, though again, not as helpful as it once was.
Any other endgame event, Blu can certainly be passable, but it's not really desired by most people, if you want to get into events, work on a support job first, if you absolutely hate support jobs, I would recommend starting with RNG, SAM, or MNK, use this to gear your BLU enough to get him into events he may not be that desired for with lesser gear, if you like.