If it changes either play time needs to be taken into account or just make all exotics acquired from xur purchase with high requirements. 3 months of raids, nightfalls, and weeklies stuff plus a 150 strange coins to get Ghorn, etc. It makes it a pain still but there is work involved unlike the rng lottery. Not every one does each raid on hard, nightfalls, and weekly strike every week. (You don't earn anything given by chance, so this lets you earn an exotic by working for it).