You can see in the image that this is very blatantly a job crystal, the symbol on it doesn't really seem to refer to anything I can think of though.


Additionally, toward the end of the trailer there's a short clip of someone sheathing a gunblade on their back, which unless DRK is getting a gunblade for whatever reason, is definitely new.

https://i.imgur.com/bZienDv.mp4

In my opinion, if the (likely) new job is indeed a gunblade user, then it's probably not a healer, and the fact that we've already seen two DPS jobs introduced this expansion means there's a solid chance this is a tank job.