Less xp for lower level mobs
Currently, the quickest ways to level up are to kill chickens in spawn, or possible by boosting players. Therefore, it would be a nice feature if you gained less xp for different leveled mobs.
This would mean if a player is level 10 and kills a level 2 seagull, it gives less xp than a level 2 player killing a level 2 seagull.
Same goes for a level 2 "killing" a level 15 monster with the help of a party member.