The XP system is literally pretty easy to fix IMO.
Its fine that they want to award XP for completing challenges. 343 can keep challenges in. But the challenges need to be broader.
For example instead of have a challenge for kills with mongoose, just make it kills for vehicles. Or instead of kills with Mangler, just make it kills with a pistol. Ground the challenges together. This allows players to play towards the style they like. As opposed to forcing the player to play how they don’t want to.
But there absolutely also needs to be XP given for playing. For example:
XP could be given for winning the match
Getting MVP in the game type your playing
Even say 25 XP for playing a match.
Whatever happens I think this is crucial for making the teams play to the objectives. And giving the player a feeling if accomplishment.
As it stands the gameplay itself is fantastic and is so fun to play.
But the XP progression needs to feel doable. As it stands it feels out of reach. And currently encourages players to ignore the game objective for the team and focus on doing there own thing for the sake of XP.
343 you have a great MP game here. Don’t let it slide by with this current XP system.