LDR 5001 is better than Ice Breaker on hard Crota when using the middle strategy as it penetrates the rocks the swordbearer hides behind. Thus with a legendary primary and secondary you could use DB if you don't have the Ghorn. I have not tried it because I have a maxed HoC but I do find the DB is best for the Deathsinger fight and it would be fine for Crota as long as you have good aim and timing of your shots to avoid missing him.