Hi Dice, this is my solution to XP farming servers issue, you are Welcome!
First thing first, farming is just part of the game nowadays. You don't want it get out of hands or nerf it to the ground that player lost motivation to play your game, which is you really need.
So first, XP Progression:
1. AI Soldiers do not count towards ribbon Progression in All Out Warfare and Portal.
2. For Player custom made servers in Portal, Set a Daily XP Cap and a gloabal XP modifier of 0.8, that's 20% less than normal. The Daily XP Cap is PVE XP 20K, PVP XP 60K, in total 80K XP. Player will receive significant less XP afer reaching the Daily XP Cap, which is max 500 XP per lost, 900 XP per win upon match completion.
3. Featured playlist in Portal and solo coop in All Out Warfare is unaffected by Daily XP Cap. Featured playlist inclues 3 classic modes and community high light modes.
Mastery Progression:
Mastery progression mostly based on kills, I'll call it mastery point, for example 1 kill equals 1 mastery point.
1. For PVE(against AI Soldiers) Daily Cap is 30 mastery points per mastery entry, and a total of 150 mastery points, player will not receive progression after reaching either cap. This applys to All Out Warfare and Portal.
2.For PVP(against other players) on Player custom made servers in Portal, Daily Cap is 300 mastery points, no limit on mastery entry like in PVE.
Hazard Zone is unaffected by above changes, Occupying Forces(AI) is treated as player for Progression. It needs to be more rewarding for people even care.
Daily Cap maybe not the best solution, but it's simple and effective, what ever route you choose just be clear about it.