Probably going to. I haven't even playing multiplayer (no friends) so it wouldn't have anything to do with that. I started my first save with Zane. I'm just at about 70 hours into that save (completed normal and TVHM, maxed out level 50, farmed 100s of legendaries and got to Guardian rank 220. Sometime last week I was getting bored and decided to change to a new character to play the game a different style. From that point till now it's been zero level XP from any enemy I kill. Doesn't matter the level, it's been this way since level 1. Any enemy xp goes to my guardian rank.

I personally thought it was just dumb game design and you just had to deal with it. But now that I have you and another person saying it's not that way I'm realizing it's probably a bug. Makes more sense in hindsight now as it's super hard to level up just on missions alone. Really sucks not getting xp from enemies.