I’ve cleared torghast no problem as shadow. It’s really just all about the anima powers.
Anyways this is the build I use for solo play and torghast.
Fortress of the Mind for torghast and works well with the anima power that makes our mind blasts instant casts while power infused. Death and Madness is not really what you want to be doing in torghast. But it’s good for dungeons.
Misery,
Psychic Horror
Shadow Crash
Surrender to Madness
In general, it’s bad rule to make big pulls as shadow in torghast. You can do it easily enough on the lower floors but as you get higher they just have too much HP. It’s not worth risking it. So it is a slow process if you want to play shadow in torghast.
Shadow aoe in general is not good. You have to devout all your talents to it or you’ll fall behind everyone else. Mind sear only gets good with searing nightmare now and feels very underwhelming without, but you’re not going to be pulling large enough packs to make it worth using 90% of the time. Even in mythic+ pugs right now people aren’t pulling large enough packs to justify using searing nightmare. So misery is the better option with surrender of to madness to keep higher void form times up. Surrender to madness is particularly good in solo play as more void forms is never a bad thing.
So your opener will look like this. Save insanity for pulls. VT, VT, VT, DP one target, shadow crash, void torrent, dp, void form, void bolt, mind blast, mind blast, void bolt. You can mind sear here as filler as well, but if you’re doing it correctly, you won’t really have time to mind sear because you’re always casting one of your big damaging spells. This really only applies to 3 targets or less. But it should give you some concept of what you should be doing.
Weaving in DP so you don’t cap insanity, and keep it rolling on one target as you burst it down with your bigger damaging spells.
Anyways, go to warcraftpriest website, then go to shadowpriest guide for shadowlands through the tabs at the top. Also, recommend joining the shadow priest discord. They’ll probably do a better job of explaining than I did.