In past two months i’ve leveled 3 alts to 70. And out of all specs - SP is the one i haven’t seen in dungeons even once.
Maybe that’s because they don’t have aoe and extremely mana hungry so people just not finding them fun in group content.
I have a 61 shadow priest (was my first vanilla classic character actually) and honestly i don’t want to level him up, even just killing mobs in hellfire feels meh
AoE is one among many issues.
DoTs are pretty much useless except for boss fight where I was top DPS most of the time. (Normal or Heroic dungeon)
And the change to Vampiric touch between Tbc and Wotlk (“1% mana per 5 sec for x sec when using Minding Blast” instead of "5% mana from any shadow damage dealt while active) made us pretty much useless now lol. I didn’t have difficulty finding a group, but I’m definitely less useful than I once was.