I play the pvp weeklies on a tank in 332 mit gear, can usually protect for around a million if i am near the bulk of the fighting.
tl;dr:
My experience in 4x4 arenas is that if my team wins, i will usually get 8 or more medals. If my team loses, i get anywhere from 0-4 medals depending on how bad we lost by. The arena map doesn't seem to matter.
For warzones, I can usually get 8+ medals when my team wins, but it varies more per map. i can consistently get the 2 tank medals (protection overall, protection in one life) if i am in the fray, the damage in one hit medal rarely if i crit on someone who is already sundered and taking extra damage, the rest of the medals i rely on either camping an objective for defense medals, or hoping that we win super fast to get the early win medals.
alderaan/yavin
If i rush to cap the turret that is our side and then babysit it for defense points, i can usually get 6-8 medals. If i run to other turrets to help cap those ones, i will generally only get 8+ medals if we get the early win bonus ones.
novare coast
this is another one where i can get close to 8 medals by standing around a captured turret all match. I don't think i've seen early victory bonus medals awarded here.
voidstar
I usually get 8 medals on this because everyone fights near the doors and the defensive points roll in, the early victory medals here can add up quickly when the team that attacks second is way better than the team that attacks first.
hypergates
If we get our pylon early and i camp it for several rounds, i can usually get 5-7 medals but generally need at least one of the early victory bonus medals to get 8 or more. And the medals don't seem to reward strategic play like denying the other team pylon/orbs or defending your teammate who captures the pylon. Sharing the capture pylon credit with nearby teammates like alderaan/yavin do would be very helpful here.
huttball
the only time i've gotten 8+ medals here was when i got grouped with a half premade and they got max points in a couple of minutes so all the early finish bonus medals floated in. I usually get 0-2 medals on a loss or 3-4 medals on a win here. This is the least fun map to play because i feel like i'm going to get stomped with nothing to show for it.
odesson
This map comes up so rarely i feel most players don't know what to do. I spend more time trying to explain how to play in ops chat than i do actually playing. I do like that the active zones move around so offensive/defensive play isn't just standing in the same spot all match but instead i spend a lot of time wandering hallways trying to figure out where to go instead which feels even less productive, medals wise.