My petattack macros all go thusly:

/assist focus
/stopmacro [noharm]
/petattack
/cast mark of ruination
/cast emote of pwnage
/cast money grubber
/etc.
/ad nauseum

The key being the "/stopmacro [noharm]" which prevents nasty unwanted side-effects of the automatic targeting aspect of /petattack. /startattack suffers from the same problem, so I have the /stopmacro [noharm] in a lot of my macros.