Perhaps the most elusive of all tanking stats are the various magic resistances. You can't get them on any of the normal gear you strap to your various extremities, only on some trinkets. Some races have magic resistances as part of their racial bonus toolkits, but these are minimal and don't stack with any other resistance buffs. And speaking of which, two raid buffs -- Mark of the Wild and our own Blessing of Kings -- will increase all magic resistances by a set amount. Lastly, you can buff your resistances by a rather large amount with an elixir.
It fits that resistances are so rare considering how very, very powerful they are. Just the combination of a Prismatic Elixir and a raid buff can be worth about 28% magical damage reduction for fire, frost, and shadow damage, for example. Combine on top of the that the clicky effect from Mirror of Broken Images -- Image of Immortality -- which is worth 40.51% damage reduction by itself, and you're talking a serious percentage of magical damage just brushed off like dust on a sleeve.
A short history of magic resistance
In the early days of WoW, a key gear check for some raid fights was the requirement that everyone in the raid had to accumulate a set of gear with resistance stats for a specific type of magical damage. Molten Core was obviously the first, requiring raiders to grind out a complete fire resistance set so they could withstand the various fiery attacks that Ragnaros' minions would dish out.
This trend continued throughout vanilla WoW to fights like Princess Huhuran, for whom you needed melee players kitted out in nature resistance gear, to well into The Burning Crusade for fights like Hydross the Unstable. There, the encounter demanded one tank in frost resistance gear and one in nature resistance gear to correctly tank the fight. Black Temple had several fights that rewarded shadow resistance, and perhaps the grand swan song of the resistance set in The Burning Crusade was M'uru.
Wrath was decidedly muted when it came to requiring magic resistance gearing for the raid. Early work on Sapphiron was greatly facilitated by it but was quickly made obsolete with even a smattering of gearing. Perhaps the last fight in WoW to call for a resistance set was Hodir, but again, that became unnecessary quickly with enough gearing. In Icecrown Citadel, only Sindragosa really needed resistance gear, and that was purely for the tanks to help mitigate her frost breath.
It was evident as Wrath marched on that the thinking at Blizzard had changed. Resistance gear was on the way out. It was boring and cumbersome to require a raid to grind out a set specifically needed for a single fight (or maybe two), and ultimately, the whole concept was just not fun. And so the whole idea of magic resistance shifted on its axis away from being a requirement and toward being a bonus.
Cataclysm was the pilot run for this new way of thinking. There were no new resistance sets for any magic type. Instead, there was an incredible new trinket available on Tol Barad, the Mirror of Broken Images -- a very compelling reason to grind the dailies in that hellish place. In addition, the Flask of Lesser Resistance was upgraded to a more powerful (and guardian elixir) Prismatic Elixir.
To be fair, this idea of magic resistance as a cooldown was first conceived in Wrath when Aura Mastery was introduced, the most useful incarnation of which was when paired with the various resistance auras. It was so powerful that any paladin spec was often cajoled into talenting into it, which eventually forced Blizzard to restrict it to holy paladins only so that it wouldn't be so widepread. But this was just baby steps.
Nonetheless, come Cataclysm, magic resistance stats were a completely different animal.
The trinkets that never aged
In Cataclysm, many of the boss fights had their most deadly damage coming from burst magic attacks. When you can use the magic resistance stats to shave scores of damage right off of the heaviest hit being dealt, you're clearly looking at a very critical stat for tank survivability.
It's been fun watching the arc of the Mirror of Broken Images' usefulness as Cataclysm continued. And by arc, I mean a sharp ascent followed by a straight horizontal line right into the future. Across every tier of this expansion, the Mirror has been the go-to trinket for paladin tanks, not only for the wonderful on-use effect but also because of the impressive chunk of mastery it would bestow.
Personally, even when block-capped, I built my gear sets around the assumption that I was using the Mirror of Broken Images. It was so powerful that it was a must-have to use on just about any progression fight.
Moreover, on the cutting edge of progression, some tanks even went back to their unvendored Sindragosa's Flawless Fang and paired it with the Mirror. Using one trinket and then following it with the last gave tanks a massive chunk of magical damage reduction for at least 20 seconds every minute. Even well into Dragon Soul, such a possibility of survivability boosting in the face of overwhelming magical damage was too good to pass up. They could also stack, but chaining was usually the more powerful option.
What does the future hold?
Knowing what Blizzard knows now about how highly tanks value these trinkets, Aura Mastery plus Resistance Aura, or any other source of magic resistance, the big question is whether it will repeat the move of giving out so much magic resistance in such small packages. I can't help but think that there's no way the developers would be happy about watching tanks use the same trinket for all three tiers of a single expansion, not to mention reaching deeply into their banks for a similar trinket from the last tier of the previous expansion. If I had to assume -- and I suppose I must -- I think the devs will take steps to curb magic resistance's power in Mists.
It may just by not itemizing any future One Trinket to Rule Them All or something more definitive like the massive nerf that the various bonus armor pieces of tier 10 took with the advent of Cataclysm. As someone who's ridden the resistance train as far as he could -- as runaway as it might have been -- I'm a little wary of where the track will finally run out. Still, what a ride it has been. It'll be interesting to see where it reaches next.
The Light and How to Swing It shows paladin tanks how to take on the dark times brought by Cataclysm. Try out our four tips for upping your combat table coverage, find out how to increase threat without sacrificing survivability, and learn how to manage the latest version of Holy Shield.