Or alternatively, kills vs real players should be valued higher than bot farming.
Playing Lone fighters is already like shooting yourself in the foot - you enter a way more challenging experience yet get way less XP (because naturally you get less kills).
With the recent patch the devs cracked down on custom games XP again, by removing (for now, what seems like for matches under 10 players) battle hero and victory multipliers. For some reason 5v4 Lone fighter matches will get the bare minimum XP now.
Devs, if for some reason you really hate people leveling up in custom games vs bots (your fault, not the players’, the game’s progression is incredibly, painfully, unreasonably slow and lackluster for F2P players), make it so bot kills give less XP per kill in custom games, but human player lobies can still get full (actually, must be higher) XP amounts.