The way the game is designed, it's near impossible to have a 'support' class.
All characters have access to six in-game consumables. Classes with already high weapon damage (infiltrators and some soldiers) have debuffs - not one or two, several of them do (HI, DI, SI, GI, AIU, QMI among others.). There is not much room for support characters to dominate.
BW tried a little bit with powers like shield boost, juggernaut's squad command and debuff focused engineer, demolisher with supply pylon etc. but it doesn't work. One way a truly support system could work is if characters actually need to depend on others e.g., don't give infiltrators debuff powers, high DPS characters shouldn't be able to carry as many ops packs/gels as others. What if an infiltrator couldn't carry max ops/gels and had to rely on others? What if damage cloak doesn't actually make you invisible and merely give you damage boost and temporary DR?
I'm just randomly blurting out stuff - these may not work. What I'm trying to say is that the game's design prevents 'support' characters to shine. If BW wants to have support characters like medic, ammo supplier, etc., they must actually make the game a lot more co-op in nature.