Since Spell Lock is on the GCD shouldnt this work?
/cast Spell Lock
/cast Grimoire: Fel Hunter
Not spammable though.
Personally I play with Spell Lock on shift+E and Grimoire: Fel Hunter on ctrl+E
For some reason the autocasted interrupt when casting Grimoire: Fel Hunter is not reported in the combatlog en therefor not being reported in /say chat bubble. Very irritating.