So, anyway, I'm only able to pull about 4500-4600 on Patchwerk without any consumables, yet I'm seeing Priests in equal/less gear pull upwards of ~4800.
At the moment, I have 2417 static (Illustration of the Dragon Soul) spell power. Our raid has no Elemental Shaman, so I'm losing ~80 spell power from Totem of Wrath. I have 16% crit and 477 (14.5%) haste. My spell priority is obviously fine. One of the Shadow Priests I'm comparing with has roughly the same gear I do (a bit less), but he replaces the Illustration with a second spell power proc trinket. His DPS is nearly 4900. I lost the WWS, unfortunately.
My DoT uptime is around 96%. I'm losing a few ticks of Vampiric Touch, but it's usually better to lose that portion of a second getting a Mind Flay tick off than it is to wait a second, doing nothing, so I don't clip VT.
Exactly how much does a flask, food, and popping a potion increase DPS by? It seems unrealistic to think it would increase it by that much.