It hasn't been diminished by Abyssea, it's been diminished by the level cap increase, mages getting more sources of refresh, and mages being able to sub rdm and gain access to both Refresh 1 and convert. Refresh 2 isn't necessary for a Whm to keep up healing outside, and still be a better healer. Sch is still a far better nuker and both are better at enhancing spells bar 1, Phalanx2, which Sch/Rdm can AoE the single target of. Inside Abyssea even with a melee buff, Rdm still won't be wanted for much aside addle until Whm gets it. Outside, possibly depending how big the buff is, would just make the job viable for something that 3 other jobs don't outclass it in when it comes to backline mages (1 in frontline mages).
So RDM has had what... 9 months not being the most demanded mage in the game?