Glyph of Felhunter is bugged, giving 20% damage to all warlock pets. Similar bugs like with ignite/combust and warrior’s fiery weapon/deep wounds interaction were fixed very quickly. Demo is the most powerful spec in the game by a mile on single target and has been empowered by this bug for 6 months now. Fix it.
Now stack it with Incubus Lash of Pain.
Yep, bugged glyph buffing a bugged pet.