Yes you can. Only place you can get them. And I'd definitely stick with what you're doing, you don't wanna start the dlc on ng+. Even on a first playthrough, the dlc bosses make the regular game bosses look like they're in easy mode. But if you get the flaws and beat a certain dlc boss, you'll get a rune that enhances the claws. Makes them really fun. You running a specific build?