A support role wouldn't be useless, it just has to be implemented correctly.
For example, 4 man content would have to be retuned to 5 man content, 1 tank, 1 healer, 1 Support, and 2 DPS, and so forth. Otherwise, the Support would have to count as either any of the other roles which would then make the support a ghetto version of whatever.
Then there would have to be at least 2 dedicated support jobs, to at least ensure that there are enough supports running around to actually do stuff. Then finally the whole balancing act where the game has to be rebalanced to take into account that these characters are going to be around to buff everyone else.