Schizophrenic set design

The Hunter’s Mark recently discussed hunter set bonuses, so I'll do the same for mage sets.

As a rule, mage set design has always been.. schizophrenic. There's the sets with simply awful bonuses: Magister (dungeon set 1), Sorcerer (dungeon set 2a), Ironweave (dungeon set 2b), Vaulted Secrets (AQ20), Incanter(dungeon set 3a). People who designed those sets have no idea of overall mage gameplay. No intelligent mage is going to stand still and let his Mana Shield absorb hits while chaincasting Flamestrike. Not only it's suicidial, it also fails to provide adequate DPS due to having to recast Mana Shield. Even a Mana Shield amplified by set bonuses is only going to take 2-3 hits at most from non-raid mobs before crumbling, which means you have to recast it. Recasting Mana Shield leaves no time to take advantage of the reduced cast time on Flamestrike, so you end up doing minimal DPS and using all of your mana while doing it.

Then there's the okayish sets, like Arcanist(tier 1), Enigma(AQ40) and Tempest(tier 6). Definitely worth collecting, but could be eclipsed by careful itemization. If you head to Molten Core wearing Magister, Arcanist is certainly an upgrade. It's less so if you have cleared Zul'Gurub or gotten most of the better level 60 blues. Still, the decent 8-piece bonus of -15% threat helps a lot.

Enigma has a spec-specific set bonus, but makes up for it by having pretty hefty stats and a nice proc for boss fights if you didn't have Spell Hit capped (most mages didn't).

Tempest is currently the set with the highest itemlevels of mage gear, so it's best by default. It might eventually be eclipsed by stuff that drops from the Sunwell Plateau, but will hold up pretty well until that. The 2-piece bonus is a bit underwhelming when compared to the equivalent Frostfire one, but the 4-piece bonus is exactly what mages need: more damage.

Then there's the nifty sets, worth having for simply the set bonuses: Netherwind (tier 2) and Frostfire (tier 3). All set bonuses are useful and the items themselves are nothing to scoff at. Furthermore, the set bonuses are useful for all mages, regardless of spec.

Finally, there's the bizarre sets. Aldor (tier 4) is mediocre as a PvE set, but has a few of the most useful set bonuses ever for PvP. Pushback immunity and shorter cooldowns on PoM/Blastwave/Ice Block. Either of those bonuses would have been welcomed with cheers if those were put into the Gladiator set(s).

Then there's Illusionist (Zul'Gurub), an another oddball set. It has the bread-and-butter spelldamage bonuses, but then mixes the promising set up with reduced mana cost to buffs and Flamestrike cast time reduction. Even pre-nerf, Arcane Intellect and Arcane Brilliance mana costs were a non-issue. When you are buffing, you usually have plenty of time to do so. And since you can conjure your own mana drinks, you always have ample mana. Then there's the Flamestrike bonus. An okayish generic set which has a spec-specific set bonus in the end? And to get the said set bonus, you have to wear Hazza'rah's Charm of Magic, which boosts Arcane damage, not Fire. Is Illusionist a generic set, a fire mage set or an Arcane mage set? I really cannot say.

Finally, there's Tirisfal (tier 5). If there ever was an argument why mages should get alternate sets like most of the other classes, Tirisfal is it. It's exclusively designed for Arcane mages. For all others, Arcane Blast not only provides substandard DPS, it also is an order of magnitude more expensive than the other nuke spells (Fireball, Frostbolt). No sane frost/fire mage would ever want to make it even more expensive.