They have way too much health. Change the class skill from a health buff to a damage reduction vs. bots and turrets. This way it is a bit more fair to deal with supports near firebase. And even though they'll have less health the damage reduction will allows them to do their job as a support who wants to hack stuff or escort bots.
I think the supports health is fair being on the medium pro health tier with the assault. If anything is adjusted, I would say how ridiculous a 3.3 firebase is. That thing can SNIPE! But seriously its range covers about half the map, plus it can take out a tank in no time
Your probably playing against a Custom Support w/ a Gold Armor Upgrade, from my playing a support (just about 1 billion heals now), i can tell you, if you think they have way to much health your either playing against someone w/ a gold or silver armor endorsement, or someone who is heal/drain gun kiting you. As for Turrets sniping, easiest way to take them out is w/ an assault/gunner/tank/sniper and using a mix of grenades/mortar/railgun/sniper rifle and outranging it and taking it down. These things aren't overpowered, they're working as intended and how they should.
