True or False, folks: Arcanist, with its threat reduction set bonus, is critical to success for newcomers in BWL (who are not geared in Netherwind).

you can just look at the how it went with horde v alliance pre tranquil air. There were still horde that progress very rapidly. Now there is a tranquil air totem on horde side which will make learning the instance easier(to some much easier). I dont think blizzard will ever make a set bonus imperative to learning an instance.

Only two mages in the guild bothered to complete the Arcanist set, and I think it only really helps in the Broodlord fight -- elsewhere it's absolutely unnecessary, and you only gimp your damage output by wearing it. And even in the Broodlord fight, you end up spamming Arcane Missiles(with 3/3 in Subtlety) out of habit and a desire not to screw up a kill and force another 20 minute re-clear. And really, if that's all you end up doing, you don't really need to wear 8/8 Arcanist anyway, since the 40% threat reduction is enough (and with an additional 20% from Tranquil Air nowadays, the only way a mage will pull aggro is if the healers suck and let all the tanks die).

False. I've written up a couple long summaries about the arcanist set, because I used the 8 piece for a long time. If you respec subtlety than there's no need at all and you gimp your damage potential by a lot as falc said already.