Maybe link it to K:D of the team and how well they are doing.
Start of round teams start with x3 (Higher than average multi gained playing battle), If your team's K:D goes positve (1.5:1) this drops to a x2 and the other team raises to x4. This encourgaes people not to quit when loosing and seems harder to abuse than some other systems. XP is only gained when a certain number of kills are achieved per minute.
Logic behind this is that the team which is winnign in the fight would not mind being on a lower multiplier as they are currently dominatign the other team, in a balanced fight where the K:D is balanced then players will recieve more XP than playing on battle servers and players are less likely to quit when their team is loosing in strategus as they recieve a good amount of XP.
The abuse for this system would be to just intentionally throw the match, especially in a village defense. "I don't care about this village, I just want my x5! CHAERGE!!!" Some people would try to make your team lose because they'd rather have the loser reward than the winner reward (or they realize they are going to lose anyway and just want to maximize it).
I don't think K:D should be used as a measure anyway. If you get to something like 200 deaths and 50 kills, you know that's probably not going to get turned around to anything positive.
...
Actually, what COULD work and might be an improvement over my original idea as well is a minute-by-minute K/D reward system (or, say, K/D calculated and reset every 3 minutes).
So during this 3 minute period, your team's K/D is 3:1. Big reward.
During this next 3 minute period, your team's K/D is 1:2. Smaller reward.
It could be something like:
(no kills) = x1 multiplier
1:3 KD or worse = x1.5
1:2 KD = x2
1:1 KD = x3
1.25:1 KD = x3.5
1.5:1 KD = x4
2:1 KD = x5
...?
("0 deaths" would be treated as 1 for the purpose of K:D. So 3 kills and 0 deaths = 3:1 reward.)
We could also take an element of my "kill density" concept and say that for the x5 reward, you not only need a 2:1 K/D for your team, but you also need to have killed some minimum number of enemies (perhaps a percentage of tickets, or a percentage of people on the roster. That way, if it was 50vs50, you can't just literally kill 2 people and then hang back -- you'd have to meet the K:D requirement as well as a minimum kill rate to qualify.
The point of resetting the K/D calculation is that even if your team sucks it up for the first few cycles, you don't need to overcome your total K/D, which is in the pits -- you just need to do well for the next cycle.
In summary, I vote we just lock chadz in a room with no food until he comes up with a solution. I predict it will take no more than 6 hours.