If that is the hybrid they had in mind then it's never going to happen. There are some cases where DPS can relieve a healer, namely with Vercure, Clemency, and Revival abilities, but making a job capable of pulling 2 or all 3 roles is just asking for too much. Even if SE did decide to do such a thing, it would be way too stretched out to be acknowledged by endgame meta, and making it potent enough to run endgame would make it OP. FF14 cares too much about the role trinity to just throw a screw like that into it.