Havent played much since the lib patch, but i noticed that kill assist XP are alot lower, i.e. only 80XP for MBT kill assist. Critical kill assist is also bugged, i.e. i got only 10XP for phalanx turret kill assist, although i did ~90% damage to it.
This will be fixed in this week's patch. It will still be a scaling system (which is a good thing), but with the total assist XP pool adjusted to be more rewarding
The same was true before the change. You had to be among top 3 (2? 4? i dunno) contributors to get assist XP.
I rather like that the assist XP is damage based instead of a flat base. It's more fair in the long run if they get it working correctly