I think Dragons breath is a great weapon. I think it's underrated and gets a bad rap, However, it is much more situational and has drawbacks. The good: It's great in crota's end for taking down shriekers, Ir yut when she's casting liturgy and keeping doorways and other area's clear of enemies. (like shooting it at the doorways for Ir yut can keep knights and acolytes off you back. The bad: no tracking means your aim has to be spot on, and the flare will make crota and other enemies move. Honestly I think it's worth buying and worth using if you don't have any of the others. But I also think for crota himself it would be better to use a normal legendary rocket launcher with tracking OR proximity detonation (I think proximity takes a bit more skill but is just a viable. also I think proximity is generally way better for pvp.)