I'll start with the epic "tier" raid sets, since those are the most discussed. The picture at the top of this post shows Tiers 1 through 3, from left to right.
Tier 1 is the Vestments of Prophecy. It has eight pieces and drops in Molten Core, one piece off each boss except for Ragnaros and Majordomo Executus, and two pieces off random trash (those are bind-on-equip). It's epic, although for the stats it hardly beats many blues. The set bonuses are a bit odd:
- 3/8: -0.1 casting time to your Flash Heal
- 5/8: +28 spell crit
- 8/8: +25% chance to crit with Prayer of Healing
Personally, I'd say the 3-pieces bonus is the only one I'd really try for -- I'm convinced it's saved my butt a few times -- but the 5/8 wouldn't be bad to have either. I never found myself using PoH in MC, so I'm not sure what's up with the eight-piece.
Overall, the stats heavily favor Intellect (170) over Spirit (117), which makes sense in the flash-heal based model of yore, but is annoying in light of today's Spirit-loving Priest builds (at least my own), which came into being long before BC was released and hence when many priests were still looking at level 60 epics. Still, at this point it hardly matters. Most of the set is pretty useless to shadow priests, but a few pieces have +damage/healing instead of just +healing: the wrists, belt, and shoulders. Looks-wise, the only thing of note is that the pieces that hang down from the shoulders turn to follow your camera as you move it. Try it, it's weird. Especially impressive from above.
Tier 2 is Vestments of Transcendance. This eight-piece set drops mostly in Blackwing Lair, with the pants coming from MC's Ragnaros and the headpiece coming from Onyxia. The set bonuses as they stand now:
- 3/8: +20 mp5
- 5/8: When struck in melee there is a 50% chance you will fade for 4 sec
- 8/8: Your Greater Heals now have a HoT component equivalent to a rank 5 Renew
It would be remiss not to mention, however, the former three-piece bonus of Transcendance: 15% of your mana regeneration from spirit is active "while casting" (which means "inside the 5-second rule"). Essentially, this bonus was so powerful that Blizz was really worried priests would want to keep 3/8 Trans over BC epics, so they nerfed it. And they were right, too; if I'd had 3/8 Trans I probably would have been intending to keep it over some Karazhan pieces, especially considering BC sets are only five pieces.
The five-piece bonus on Trans is generally considered lacking, as far as I'm aware; if you get hit in a 40-man raid, you're probably dead already. The eight-piece, however, always looked pretty nice to me: free heals are never bad. Renew 4 is 245 healed over 15 seconds. Stats-wise, Trans still favors Int over Spi, but not by as much as Proph: 176 Int to 127 Spi. In fact, Trans is pretty close to Proph on most stats, with something like a 10–20% boost. +Healing, however, is the exception; Trans jumps Proph's +healing from 134 up to 300. On the other hand, there is absolutely no +damage on the T2 set, so Shadow Priests in BWL, you're out of luck. (Yes, I'm still talking to the past here.) For some reason the looks remind me of Starcraft, but it's not a big deal. Overall a big graphical improvement on T1.
Tier 3: Vestments of Faith. This is the first set released after the 1.10 Priest revamp, and it shows. Like all the other T3 sets, this is a nine-piece, adding a ring to the eight slots of the other sets, although the highest bonus is for having 8/9 pieces. The tokens and pieces for it drop in Naxxramas, with the ring dropping off Kel'Thuzad, the final pre-BC boss (perhaps an honor shared with AQ40's C'Thun). Some crafted items such as Mooncloth are also required to get the pieces. Faith breaks with the 3-5-8 set bonus pattern, offering four bonuses:
- 2/9: Reduces mana cost of Renew by 12%
- 4/9: Greater Heal crits give your target Armor of Faith, absorbing up to 500 damage
- 6/9: Reduces the threat from your heals [by 10%, as far as I can tell]
- 8/9: Each spell you cast can trigger an Epiphany, increasing your mana regeneration by 24 for 30 sec.
Every one of these bonuses is quite solid: efficiency, bonus healing, efficiency, and efficiency. This is great stuff; the only problem, of course, is that the vast majority even of raiding priests have never and will never see it. For my money, the 8/9 bonus is the strongest, though the 2/9 is a contender. As far as stats go, finally we see Spirit given decent footing: 173 Spi, 190 Int. All stats are significantly boosted from Trans, to the tune of 30%. This was basically the reward for beating the game, pre-BC. And you can't beat its looks: you finally get a freaking halo. Awesome.
But what do you collect before you're ready to hit the mean passageways of the Molten Core? Dungeon Sets, of course! Pictured at right are Dungeon Set 1 and Dungeon Set 2, a.k.a. Tier 0 and Tier 0.5.
In theory, the dungeon sets were supposed to be a good preparation for raiding. However, in practice (not that it matters much any more), a priest could put a much better set together out of mismatched blues (from Dire Maul or, later on, Blackrock Depths, for instance), and do it easier than trying to collect every piece of the Vestments of the Devout, our T0. The set drops all over the place (Scholomance, both sides of Stratholme, and Blackrock Spire). Like the other T0 sets, it carries no class restriction, though this led more to shadow priests wanting the Warlock set than to anyone else wanting ours.
The set bonuses are as follows:
Sadly, none of these bonuses are particularly worth worrying about, although +23 damage/healing can be a nice boost when you're a fresh 60. Stats-wise, it's fairly trash, as I mentioned before, although it does have a decent amount of Spirit (only two less than T1, in fact). Of course, if you're wearing T0, you're probably doing 5-mans in which case you want more Int anyway...ah well. All in the past now.
And what's this T0.5 thing, you ask? Well, it was Blizz's way of giving the casual PvE players a way of upgrading their gear. You take your T0 pieces, your Devout, and embark on a series of quests, upgrading the pieces in turn until you wind up with the T0.5 set, Dungeon Set 2, Vestments of the Virtuous. Congratulations, you now look like french toast. The set bonuses are the same as T0, just in opposite order:
2/8: +8 All Resistances.
- 4/8: When struck in combat has a chance of shielding the wearer in a protective shield which will absorb 350 damage.
- 6/8: Increases damage and healing done by magical spells and effects by up to 23.
- 8/8: +200 Armor.
The set's stats are fairly significantly boosted, as half the pieces are upgraded to epic quality (raising their item level, and therefore their stats budget). However, few completed the upgrade quests before either diving into raids or entering BC, since it required fairly obscene amounts of gold and grinding, both hard for the healing priest, and the final set is not particularly overwhelming. Most pieces of it aren't as good as T1, and will almost certainly be resting in your bank by the time you get any T2.
And there you have it, folks. Our Tier and Dungeon sets prior to the Burning Crusade. Which one's your favorite? Which piece had you pounding the desk in frustration at its seeming inability to drop whenever you were in the raid?