I managed to found several Core Demonology spells/passive effects bugged.
Hand of Gul'dan can be casted, but there's no point in doing it since...well...all you get is a falling meteor without the spell effects.
Demonbolt is working fine, but the stacks are fading away instantly when you switch back from your Demon form.
Wild Imps are summoned perfectly, but all they're doing is smashing the enemy for 100-140 melee dmg, instead of casting Firebolts.
The lvl 75 warlock talent Grimoire of Service is bugged. It's not even in your spellbook.
Glyph of Demon Training is bugged.
Glyph of Drain Life is bugged.
I can't really test if it's bugged or not, but the Wrathguard's main attack speed is "attack/2sec". The lvl 92 Demonology Perk Empowered Demons should make it "attack/1.8sec" . Please check it if you can.
Wrathguard is always waiting for the fading of his main attack's (Mortal Cleave) debuff before using it again, no matter how much energy he has.
Thank you for your work!