Mouseover for boss frames does not work?

[Draeblin]

So I have this macro:

#showtooltip
/petattack [exists, harm, @mouseover]; [@target]

This should let the pet attack the unit that the blizzard bossframes is for when mouseovering it. (The one for example all the garalon legs).
Problem is, it does not work.

Do mouseover macros not work for those frames; Do you also have problems with that?

EDIT: For dmg spells with my warrior it workd (heroic throw). Hm so maybe petattack broken for that (normal target works fine) or an addon.