you might want to modify that a little... you won't normally want your imps choosing their own targets

try

Code:
/petattack [target=targettartget]
/cast Shadowbolt [target=targettarget]
or if you really want to use assist

Code:
/petattack [target=targettartget]
 /assist
/cast Shadowbolt
and personally i use focus for my leader so it would be target=focustarget