I couldn't get Gally for the longest time... Now I've got one for each character and I have dismantled 6 haha.... Get on that grind son! RNGesus rewards the dedicated, not necessarily the worthy ;) There are plenty of chances to get exotics ( multiple raids/ nightfalls/ PoE/ ToO.... All which you can do three times a week... Drops increase with every dlc making it easier and easier to get exotics.