ive seen a few posts from people about drop rates but tbh i think the hardest part is getting the weapon. from what ive seen once you have a weapon its much easier to get again. For example Ghorn is rare to me because ive never had it. but ive had 5 thunderlord's 4 mythoclast's 4 icebreakers etc. However some of my friends have had that many ghorns. i think rare all depends on if you've had it yet.