I'd stick with BM for the leveling process.
I've basically got two macros which are used a ton.

#1 is:

#show Hunter's Mark
/petattack
/cast Hunter's Mark


#2 is:

#show
/Castsequence reset=combat Arcane Shot, Arcane Shot, Arcane Shot, Steady Shot, Steady Shot
/Cast [Target=PetTarget] Kill Command
/Cast Rapid Fire
/Cast Bestial Wrath
/Cast Kill Shot
/use 13
/use 14


If you're boxing five hunters, Serpent Sting won't be useful for leveling up mobs that frequently die to 5x Arcane Shot.
If you're solo, insert Serpent Sting before the first Arcane Shot.
Also Serpent Sting anything that will last a while; I've got it as a separate key that is very rarely pushed.