While my pet is attacking, he doesnt want to cast spells.
How to overcome this problem?
Eg I have this dispell macro
/cast [mod:ctrl,@focus] [mod:shift,@mouseover] [@player] Devour Magic
Its super important that the pet casts this immediately, but he won't because he's busy attacking...
Your felhunter has own GCD on abilities. When he using Shadow Bite (which starts GCD), you can't use dispell (which consumes GCD too) untill timer cooldown finished.
The only way to handle it is to turn off Shadow Bite autocast when you pretend you will need dispell, macro for it:
/petautocastoff Shadow Bite