Change your #3 and #4 macros.

Mark - 3
#show Hunter's Mark
/castsequence reset=target Hunter's Mark, Null

Sting - 4
#show Serpent Sting
/castsequence reset=target Serpent Sting, Null

You only need to fire each once.

Hunter's Mark because it should last a lot longer then the mob does.
And if you really need to reapply it, target your leader toon, assist with the hunter, retarget the mob, and you have your reset condition.

Serpent's Sting (or any sting) is reset by Chimera Shot, so you'll never need to waste mana recasting it. It will never fall off of the mob.

I would also move Steady Shot to the last slot, since that is the fall-through shot/spell, which can fire off as many times as necessary, when everything else is on cooldown. Since this spell will never be on cooldown, the abilities on #8, #9 and #10 will never fire off.

Otherwise, looks good.