Technically, when Cata's finally out and running and we're all 85s... there shouldnt be 'unforseen magical damage'
Thing is, there's a distinct lack of this so far. Dargon breaths hit about as hard as melee for every boss I've tested (I've at least put attempts in on everything but Cho'gall and Atramedes). The only times I've been surprise gibbed have been when I've done something incredibly stupid (tanking hard hitters i.e. enrages or large packs of trash w/o cooldown AND when healers aren't ready for it). I could count on one hand the number of times a tank death directly caused a wipe--"directly" meaning low dps or healer deaths didn't cause the wipe first.
Re: tanking fun, I can't speak for the other tank classes, but I know the bear "rotation" got a lot more interesting this expansion. Mostly because we just now got sword and board this expansion.
I'd gladly give up SnB for trauma Trauma (i.e. we needed Thrash way more than we needed Beserk). Right now bears only have swipe for aoe with a 6s CD, whereas every other tank has at least 2 aoe abilities (we can't even use thorns while paladins still have ret aura and warriors still have damage shield).
This game is all about execution of expected patterns. With very few exceptions there is generally only one way to get through an encounter. Survivability is a measure of how much of an error margin you have in the execution of the predicted sequence of steps (Healer DCs, is slow, some utility member doesn't do their task, a tank CD isn't used on time, whatever). This will annoy high level raiders at first, and make the end game content more accessible without resorting to instance/region buffs/debuffs. What separates a high level raider from a lower level one is the ability to figure out the plan, and to execute it flawlessly, whereas a good player will take a few attempts to learn how to do it, and some people may take a long time or never get there.
From TBC, I was an avoidance fan, and WOTLK ROFL stomped us out of existance. Simply put, Avoidance had no place in a world where tank deaths occurred in 2-3 hits that can before a healer could react (early TOC days, add a pinch of lag to healer dilemmas). If a tank can survive say 5 hits, then probability of at least one avoidance event occurring, even with lower avoidance values, is significantly higher than working with only 2 or 3 hits. By allowing us to take 5 hits, avoidance is actually an option, where it wasn't in WotLK (I was forcibly converted to EH, damnit!). I was hoping we would see a 3rd breed of tanks, mitigation tanks (stacking armor/resistances), but from what I see I doubt that be an option (paladin tanks being unhittable would be the closest thing).
I agree with Felhoof's earlier comment, they need to make gearing for the fight more important. They have started down that road by allowing us to switch specs in wotlk and now re-glyph relatively quickly (without resorting to server memory gobbling mechanism of carrying glyph stacks in our bags). Unfortunately, I predict it will be a binary choice, avoidance or stamina, as armor is now almost nigh-impossible to select as gearing strategy, and magic resistances have always been tough to do (and often ignored even by many so-called EH proponents).
The downside to having multiple sets will still be bag space (my druid carries 4 sets, a stam tank set, a threat set, a cat set, and a resto set), making more varied encounters will not help my bag space situation.
What I am noticing, is that for a while GC was annoyed that people got into higher ilvl=automatic upgrade, and yet with 4.01 changes, I have gone and thrown out most of my lower ilvl gear which was useful pre-4.01. For example, my paladin no longer uses the ilvl 200 healing libram, which was bis pre-4.01, or my twink warrior has swapped all offset gear for actual T6 because the higher ilvls meant that it worked out better for the various roles. This will make gearscore annoyances all the worse. Reforging just makes bigger stats budgets more valuable.