Just play hard mode anyway. Any 331 launcher does the job as long as everyone shoots. If the DPS isn't enough just follow up with primaries. 5 people doing this will drop crota every time. I couldn't get black hammer, did hard mode for a couple of weeks, then ran normal and it have me the drop. Crota's End is designed to give you what you don't have but will still string you along to keep playing. So go get some hard mode weapons, it might just give RNG a boot up the backside ;)