2 Key Codes and 700 XP For Coop Final Boss. Why?

Why so little? I mean you get so muhc more for doing side quests.
Another thing...I JUST made it to a major arkfall i wasnt in it for 15 seconds before it ended and I got 7000 XP and 5 Key Codes + 2 Purple Armors. My friend plaeyd the entire thing for the 45 minutes it took to beat it and got 6000XP and 3 Key Codes and 1 Green Shotgun! LMAO...I Am hoping this is a GLITCH, because its F'n stupid as hell....

Im guessing its just another problem to add to the bag of problems this game has.