I highly doubt there is much it can be used on in the raid, same as it were in past raids. It is more a PVP utility spell and not of much use in PVE. In the past when uses have been found in raids they were usually an oversight by devs and quickly fixed. You may be able to use it on trash but that would be the best case scenario.
I play a Blood DK, but on Council of Elders, wouldn't Dark Simulacrum be amazing when as unholy, stealing the shadow priest lady's Wrath of the Loa, when she's empowered. It does shadow damage, so, like Hagara and frost dks, it should be boosted by unholy mastery. You might only get one per empowerment phase, maybe two with glyph. It does 140k according to the dungeon journal, so not bad for a handful of RP.