Did some testing as I’ve never played a FO as there’s always enough of them anyway, and confirmed NeroKirbus’s figures are pretty spot on.
The most obvious discrepancy I noticed was that just topping up you team mates at spawn (all figures halved due to XP weekend) with direct hits = 60+10*4 = 280 support XP (76 for the big guy), the equivilent of 2.8 full revives (sprees excluded) before any action has even happened, lol. Full ammo restoration netted a LOT more. During my limited testing as a decidedly mediocre FO, my average round XP doubled compared to when I was at the top of my game as a Medic, and waterboy becomes a hell of a lot easy (especially with Rhinos, those eat ammo packs as a snack).
So as well as having no cool toys, being the most unappreciated and moaned at class of all with no flashy glory moments like FOp’s or Engineers they get a lot less XP for doing their job well than all the other classes…
Not surprisingly I’ve dropped my medics like a sack of hot potatoes, but please don’t inform the chumps, ah, dedicated team playing medics on the pubs of this or else seeing one especially during double XP weekend will be as likely as the Loch Ness Monster, Big Foot or a Yeti 
@Amerika_KC, Agree with everything you said except for FOp’s having a hard time completing waterboy (or rather a MUCH easier time than medics). Even with a few other ammo dropping FOp’s, racking up a nice amount of support xp with little effort is still not that hard. When your the only one dropping ammo regularly , never firing a shot with a random +25XP airstrike every now and then will probably guarentee you top of the scores (an exaggeration, but not by as much as you would think). This is acceptable to me as it encourages more balanced teams with players filling crucial roles that are lacking.
The same though is definitely not true when being the only medic, where mid table is about the best (unless rambo) you can hope for on a semi decent team while humping your arse off performing a load of revives, sprees, miracle workers, heals and assists.
@Szakalot Agree completely that it’s far more beneficial to overpromote unselfish team play than underpromote it, for the overall good of the game experience.
Hopefully this discrepency is just an oversight by SD and will be rectified sometime before medics in pubs, or rather ones that aren’t only rambos, goes the way of the dodo.