imo it's actually the reverseBand is better if you're running rain as his nuke get turned into a nova, you can use without rain as it still hits pretty hard but it's a bit slow so I suggest you use a scarf on non-rain teams as it will be faster than a lot of stuff while hitting very hard with Fishious Rend.
dracovish's strength is just barely not enough to 2HKO max defense ferro and pex without band when not in rain
however rain's added damage boost allows dracovish to meet that threshold, giving it the freedom to run scarf and outspeed and kill more mons