No, you literally went on a tangent on the different ways to use Fel.
Watch that ball of Fel consume Varian from the inside out. It grew in power not from Gul’dan, but from consuming Varian.
Regardless, we’re not fighting Varian and that vision was from Shalamayne and wasn’t his ghost.
While I do like that cinematic, it’s a little too easy to explain away as Anduin just envisioning what he thinks his father would tell him. (Only line Varian says is a repeat of a past line from Siege of Orgrimmar).
I’m looking forward to the day when Blizzard declares the Heroes of the Storm is now canon, and we need to retrieve Varian’s soul from there (old Varian intro cinematic for heroes of the storm, probably a video many didn’t see):
Easy way to explain why Varian not in SL; however, Blizzard would not just completely omitted Varian fate. He was too large of a lore character that he would not be mentioned or shown.
He was not some side character that only some players may know from lore. If he was in SL it would have been made clear were he was.