As Illana said, Glaive toss and Spirit beast is the best choice atm. You can use stampede in arena and that combined with spirit mend (pet "racial") gives you a 250-400k panic heal or offheal. Although, I've found that Power shot is quite handy in some setups where you're not the main target.
Power shot is capable of dishing out anything from 150k crits up to 200k and even 300k on some rare occasions, this makes it an excellent and often fatal opener spell.
As your playing a heavy melee cleave where your warrior and DK will take initial "aggro" I'd recommend Power shot.