So I was recently a very passionate/dedicated/theorycrafting Shadow Priest on one of the more popular TBC private servers for a while, so I have a very fresh/recent take on playing one at a “meta” level.
In Kara/SSC/TK/BT/Hyjal tiers you are extremely competitive on DPS but there’s circumstances as to why, and it’s not necessarily because “Shadow Priest > all”. It’s due to balancing issues.
One of the biggest imbalances, so to speak, of early TBC meta is that few classes have the option of crafting certain epic profession gear that vastly outweighs the effectiveness of nearly everything else on offer in that first tier. As a shadowpriest, if you want to be anything even remotely competitive, you will need to be a tailor first off, and you will be crafting the Shadoweave set (the other is Spellweave). These sets require you to be a tailor to craft and use them. These weave sets give significant advantages to those who are able to craft and use them, and thus the difference between priests/mages who craft them and those who refuse to be a tailor and don’t will be extreme. Most guilds (that are worth a damn) actually require that their casters be tailors for this reason. Not only that, but these sets massively inflate the gap between you and the other classes who do not have the opportunity to acquire or use anything similar, and this is where the notion comes from that melee “sucks” in TBC, because early on, the casters with their completely imbalanced profession gear acquired literally right after hitting 60, utterly poop on the DPS of all the melee classes who lack gear options of similar parity right as they hit cap.
As a Shadowpriest, you will literally not be replacing Shadoweave until you get to T6. That’s right. It’s that strong. That means you use it all through T4, and T5. It takes until your competing classes can get measurably geared in endboss T5 and T6 loot before they start competing with your dmg.
On the other side of the coin, Shadowpriests are extremely valuable for mana returns to their group. It’s actually very common mid-fight to swap Shadowpriests around, and or specific people in to the shadowpriest group to cultivate mana returns for those it benefits the most. Most guilds will only bring 2, at the most 3 of them to a raid though, because Warlocks are just simply better from a DPS standpoint (they can also use shadoweave), and Warlocks don’t need a shadowpriest obviously because they can tap. So typically the 2-3 Shadowpriest groups will be filled with healers. The mana return is due to the 41pt Talent in the Shadow tree called Vampiric Touch, that makes a portion of your shadow damage gives mana to your party (while also being a DoT).
The rotation is actually not complex, but I could get behind describing it as fun. It’s actually no different than what it would be in Classic, except you have literally 1 additional ability, SWD, or Shadow Word: Death. Basically you put up Pain and Vampiric Touch, put Mind Blast on CD whenever possible, and then spam Mind Flay. Rinse repeat. SWD where applicable (more on this later). The “fun” of it I guess comes from trying to find that perfect timing sweet spot with everything where you’re not clipping your dot ticks or Mindflay ticks, Mind Blast comes off cooldown just in time to be used inbetween Mindflays, and then on-top of that managing your mana. Shadowpriest is extremely mana-intensive, which means you will be spending most of your days outside of raid farming gold for mana pots, or if you aren’t a Leatherworker, using Herbing to gather mats for your guild Alchemist to make mana pots. You will go through a lot of mana pots. Even when spamming mana pots, your mana isn’t sustained and you will eventually go oom if using your optimal rotation.
The reason I said SWD where applicable, is because using SWD actually does significant damage to you as a portion of your shadow damage output, instantly, in burst. That means that during many boss fights, using SWD is a liability to your healers, and since you are not going to heal yourself and you have no passive methods of healing, you will basically slowly kill yourself or put yourself at risk of dying easier to some stray boss mechanic. Some greedy shadowpriests will find deplorable healers to keep them healed up or your raid might overgear the content to the point that they can afford it, but generally, SWD spam on CD is often advised against in sensitive, progression attempts.
When given the floor to use SWD in tandem with your optimal rotation, the damage is indeed very high for the first several tiers, but again, it’s nuanced. You go OOM immensely fast, and guess what happens when you go OOM? You stop doing damage. Guess what happens when you stop doing damage? You stop providing your group mana. Meaning, if you go OOM, you’re a waste of a raid spot. So much of the job becomes about making sure you are able to be always doing damage from 100% to 0% of the bosses’ health, which means not totally blowing your mana on your most optimal rotation all the time. You have to stretch it out, basically keep your finger off the Mindblast/SWD button occasionally and moderate their use.
Finally one of the aspects that people tend to forget or ignore, is that Shadowpriest threat/aggro is terrible. This is another thing that will ultimately throttle your damage and affect your rotation, because point-for-point, Shadowpriest threat generation per-damage point is insanely higher than other classes arbitrarily. Doing your optimal rotation will guarantee pulling aggro and killing you and other people in TBC raids where you typically will not survive a hit from a boss or raid mob as a squishy priest. So you will eventually learn to throttle yourself not only for mana conservation, but your own survival. Your threat is so immensely high, you can let the tank get a measurable lead, and still catch up quickly if spamming your optimal rotation with SWD. It’s pretty bad.
So the real challenge of Shadowpriest during encounters, imo, is challenging yourself to find the right moderation to, while popping mana pots on CD, make your mana last the whole fight, and not be too high on threat.
PvP? They’re pretty amazing for BGs because you can just run around Shadow Word: Death kill-stealing and be top of the BG leaderboard, but the best Shadowpriests stack the heck out of resilience and are basically dispel bots while spreading dots around.
Arenas though? Warlocks are more desirable. Shadowpriests basically have no defensive cooldowns other than fear on a long cooldown and guess how the rogues feel about that with their cool new ability you will learn to hate to the ends of the earth, Cloak of Shadows…