...Just checked my log, and the faction hits only come with the "spawns alone" version- the ones that stand with Shar Vinitras generate neither hits nor bumps to any faction.
Finally managed to kill a version of Sheleric Vis that counted towards the Conqueror of Akheva Ruins achievement. For me, Sheleric was in the room where Shei Vinitras spawns, but down on the floor to the right of the doorway, not up on the dais, and he was alone, not with adds.
Not sure what classifies this version of the mob as a raid encounter: the two that spawn alongside Shar Vinitras are much more difficult, both because they each have more HP than the "spawns alone" version, and also because they're there with Shar and his DoTs and slows.
Dropped Akheva blood and nothing else.
Also, there were faction hits: Akheva: unknown (it was negative, but I'm max KoS to them, so I didn't get a magnitude) Whisperling: +1 Shak Dratha: -1
Looking at my log, he had ~75k hit points, and never attempted to cast the effect noted above.
I suggest that a separate entry be made for the "spawns alone" version.
It IS a raid encounter when 1) there's only one of them up and 2) they're up on the dais with her henchmen around her. That's when she drops the good stuff.