In general, its rare, only because people don't run alot of exotic rolls. I do Nitefall Atheon hard Gorgon chest hard Deathsinger Crota normal On 3 characters every week. I used to do crota hard on all for that exotic roll too, but I dont bother anymore since I have all other hard mode loot except ship/sparrow. I've only been high enough level to run these since mid february, I have 4 Gallys.