I think Xur is a good addition to Destiny as is. Without Xur I would probably never get anything. And no, I'm not a causal. I play after work daily since launch and have had two week dry spells of exotics and when I get them it is usually a double or triple of something useless. The point I'm trying to make is that the games loot system is currently broken in that you get lucky in order to get exotics. You can't directly work towards any exotic you want with a guaranteed result. Even the exotic bounties require luck to get started with. One of the few things that are guaranteed are strange coins from a weekly. And Xur's items are bought with these coins. Which means by doing weekly heroics you know you're working towards a Xur exotic. It creates a weird balance. TL;dr Xur balances the games extremely high luck factor by guaranteeing some sort of exotic to the unlucky. Few things are earned, most are just lucky drops.