oh, important clarification: THEY SHOULDN'T BE ABLE TO REPLACE HEALERS/TANKS, but they should be able to help the current healers/tanks do better. No sub-healer/OT nonsense. Holy trinity, remember? (duh)

although to be perfectly honest, after typing that out, the amount of communication between party members necessary, and the requisite understanding of how all the other classes work (such as when they're likely to use specific CDs) seems like too much of a skill ceiling to be expected from a majority of the player base to be able to cope with. So it's veeery unlikely that the actual job will be this engaging/complex/OP/whateveryouwannacallit, but this would make it so that it manages to embody that jack-of-all-trades trait but still being primarily a DPS by augmenting/supporting all of the members of the party while not breaking the holy trinity mold.

TL;DR
Over-All Support DPS. I have a highly improbable idea of how RDM might work in game. HIGHLY. IMPROBABLE.
my 2 cents~