It's bugged. I made the report and then lost my patience like an ****t when I thought it had been passed over when in reality, it had been marked as Confirmed. I still feel like a choad.
Anyway, it's not an easy fix. I've only seen one Trinity Core server ever have it working right and it didn't last for long as that server moved into WoTLK and it was phased out. The tricky part about it is that you cast it as a 3 charge buff, it discharges for shadow damage, and when that happens you have to apply traits to it as well as confirm that you're the owner of the spell.
On Mangos it's pure hell to assign blackout, shadow weaving, shadowform damage bonus, and other aspects to sources of shadow damage that you do that aren't wands as well as being simple 3 charge buffs that hang around. You can't take a shortcut and have it trigger as a 0 cooldown spellcast as it could interrupt your wand shooting or other spell that you're in the middle of casting. It's a real oddball, a lot more complicated than the Shaman's Lightning Shield.
