I just switched from tracking the support mission over to the one where you need to play and win games of Rush and sure enough, I start getting mortar kills (even as the attacking team). I'll have to wait until my stats update to see how many I get that match but I did get the ribbon for ten mortar kills, so it must have been a good amount.
Of course you can only track one challenge at a time, which is completely lame. And it seems like you can't complete multiple parts of a challenge in one game? I played and won a game of Rush, but it only checked off the first part of the challenge.
Not only that, but something else had me wondering/fearing if it was possible: can you jump around to different parts of a challenge out-of-order or does it have to be in order top-down? Like once I complete the "Kill 20 people with LMGs" part of the support challenge, there is a bunch of other stuff and then at the bottom it says "Kill five people with LMGs in one life." Does that have to be the last thing done or can it get checked off at anytime so long as I'm tracking the challenge?
If they have to be done in order, and seemingly can't have more than one task checked off at once, and if you aren't tracking one, progress made towards it doesn't count, then I don't think I'm ever gonna net much XP off of Challenges at all. Just that I can't have progress made towards multiple challenges at once is shitty enough,nut I figured I could probably get some of them in each type of challenge. Not if some have a gatekeeper task of "Kill 'X' of enemies with a sniper rifle," since I'll probably never get any kills with one.