Oh I know that. Just that having played many (8) past titles and knowing what has worked in the past, then to see things that don't is a bit frustrating, which I'm sure you too can agree with.
And yes, you do need the bags for for ammunition/grenade recharges more than a heal. It's more so the fact the one gadget does both that's the issue.
No matter what you need, when you need it it can supply it. Double that up with the pouch which also does both and you see my point. It enables you to be hyper aggressive, with ammo and heals on demand. Support shouldn't be used for that kind of aggressive play, that is what Assault is for.
Also, people picking Support mostly for the ammunition bags. Then having the ability to revive but with no interest in playing as a medic. You now have players who are advertised as being a " medic " when they actively aren't playing that role, they get yelled at for being a useless medic and it only adds to the " another useless medic " mindset, which is also quite frustrating. Those who want just ammo, should be allowed to have just that.
And yes, I agree, all four classes need to viable. As it stands, one is op, one is reasonably balanced, one is frustrating to use since it's gadgets are ineffective, and the last is almost entirety useless except for one or two gadgets.