You have to remember that this is basically peak shadowpriest for pvp. Where one SP could hold the generals room in AV against almost any number of people.

Unless I am misremembering the patch, beyond plate level mitigation, pbaoe fear, limited healing while in shadowform, just a couple of spells required to melt faces.

Warlocks are good too, but, they require more static gameplay, as in stopping to cast. Whereas SP's are just run and gun SWP, especially if we're talking about a box setup where 5 SWP will melt people without organized dispelling. The biggest fear SP's have are melee coming in and tearing them up, but then they have pbaoe fears to deal with melee.

You MIGHT get more out of warlocks, but the effort required to leverage more juice out of warlocks would be much higher. Shadowpriests would be easy to use effectively, and would be brutally effective at just putting enormous pressure on people. It's not gonna be mage like, roll in and oh 30 people dropped dead because I caught them off guard, but, in small group stuff where you get the drop, people gonna die fast, and in large zerg back and forth stuff, where a mage kamikazi group is gonna go in, kill a bunch of people and then die, you'd sit comfortably in the zerg, and the pressure you'd put out would have the other group being pushed into Tauren Mill or Southshore consistently just because of your dot spam. Warlocks would do the same, but, because they require more stand and casting, I feel like the SP's just have that enormous mobility edge.

I guess it comes down to, do you like more stand off poke, or do you like mobility? If you wanna sync up 5 shadowbolts and obliterate anyone in a single volley per GCD, warlocks + dot pressure. If you wanna stay on the move constantly, and be basically a mobile fortress with your pbaoe fear, that applies instant and rapid dot pressure? SPs. Or if you wanna just blink in, frost nova, and then kill everyone in range of arcane explosion in 2 GCDs, then mages