"Levels" and gaining them via XP was simply a PR ploy to con people into buying the DLC under the auspices that Bungie was respecting peoples' disdain for excessive grinding. They purposely kept light-leveling extremely vague throughout the launch so people bought TTK without seeing the grind was in fact made worse than ever before. Finally, they went in after purchase, via patches to further nerf progress through the game AFTER the market saturated and the reviews were already in. They respond to every single hinderance to the player's activity as "a deep and complex bug" (paraphrased). Oddly, everything players have found accidentally beneficial were "simple bugs, easily patched over in a matter of days". A "deep bug" shouldn't actually be able to exist in the game. This company has made over a half Billion dollars. They literally could hire 10,000 software engineers to address these bugs and no lose a single nickel. The one thing not broken in this game is the PR machine running it; it's the most effective spin in the history of business.