What would be even better is a graduated SP/WP mechanics so you reward skill without penalizing lack of it.

0 - 500 WP = 8 SP/WP (4000 SP)
500 - 1000 WP = 4 SP/WP (2000 SP)
1000+ WP = 2 SP/WP

all of this + 1 SP/s in battle.

So you discourage WP farming, while still rewarding participation and skill. However, the first 500 WP gets you the bulk of your SP, so unskilled players making 0-500 WP per battle aren't totally boned.

So 1345 WP in a 10 minute battle would net you

600 WP base + 4000 SP (0 - 500 WP) + 2000 SP (500 - 1000 WP) + 690 SP (1000 - 1345 WP)

For a total of: 7290 SP

What if the winning team received a flat bonus of say 1000 SP to each player? That way you can play to win even if you don't end up earning all that many WP during the battle.

I think a flat bonus would be better than a simple multiplier of say 1.5x. A multiplier still mostly rewards those at the top of the score board.

So you end up with WP being your performance related pay and winning being a (significant) flat bonus.

It's not about reducing the incentive to AFK, it's about increasing the incentive to want to play. You can carry your team and you're barely rewarded for it(thus 5/5 although 5/10 would reduce the grind even further - the fact that we call it a grind says something in and of itself).

That being said you can't cut out those players who don't rack up the WP every game whether they are new or playing a role that doesn't give you many WP such as a dropship pilot or being a distraction. Dust shouldn't be a part time job.