Well, considering Arcane uses a limited resource {focus}, I probably wouldn't have it spammed in a string like that. Especially when it's competing with Kill Command for Focus. I haven't tested any macros on beta, but have you tried using fallthrus?

Macro 1

Code:
/castsequence Cobra Shot, Cobra Shot
/cast Arcane Shot
Macro 2
Code:
/cast Focus Fire
/cast Kill Command
You might have to swap the various "casts" around to get the best results, but less is usually more effective in situations like this.