Armor over avoidance has been recommended long before ICC.
My raid leader and I were talking after a raid and he brought up an interesting point about possibly stacking armor instead of avoidance while under the effects of chill of the throne.
He showed me something I'm surprised I didn't know -- that dodge rating (not dodge, but dodge rating) has diminishing returns. Meaning the more dodge rating I have, the less dodge I get per point of dodge rating, and despite my dodge being only 8% unbuffed in ICC, the penalty to my dodge still applies as though it were 28%.
Hence, he was wondering if maybe armor will start to have more value than avoidance as the numbers stack up. Anyone know?
I don't think anyone was stacking avoidance to begin with and has been focusing on EH. On normal modes it honestly doesn't matter but I can almost guarentee that in heroic modes EH will be the clear king since it almost always has in hardmodes.
The armor on the offset pieces are worth HUGE amounts of stamina if you look at EH and is are much better pieces than any other normal ICC 25 loot. Avoidance hasn't lost any value, going from 7-8% dodge is the same upgrade as going from 27-28% dodge.
Armor vs Avoidance is not usually a choice. You can't particularly gem for Armor (except through Agi), but you can for avoidance.
If you're talking trinkets though, see Karlhungus's comments above.
Also, for some light reading:
It is a choice as you collect gear. For example, I swap between the Marrowgar tanking neck and Legionnaire's Gorget depending on how much armor I want to stack. Similarly, I'm sure some people have pieces like the Clutch of Fortification or the bonus armor ring off Twin Valk's. Trinkets are the easiest place to swap, but it's not hard to "stack" armor as an ICC tank.
My current qualm is the frost emblem chest. It has an amazing amount of stamina & armour, but no dodge or parry (I know the defence adds avoidance, as does the expertise indirectly, but still). I suppose I can compensate by wearing my Corpse Tongue Coin - Item - World of Warcraft (Which I quite liked using on festergut) if I feel I need the added avoidance sometime.
Technically this isn't true if you use a bit of logic. Think about Tank A going from 0% to 1% avoidance and then about Tank B going from 101.4% to 102.4%. Lets get hypothetical. If the boss does only avoidable hits, Tank A's healers aren't going to notice much of a difference in healing him. On the other hand, Tank B's healers are going to be bored because he won't take a single hit, so long as he doesn't turn around. Of course, the only boss I can think of that did a string of only avoidable hits was part of the Req of Souls(I think) encounter in BT, but that's besides the point.
True but from a warrior stand point its impossible to realisticly reach unhittable in a normal EH gear set.
Even without looking at the extreme ends, it's still true. The reason that avoidance has a DR curve is that adding a 1% avoidance has more value the more avoidance you have.
Ie. 50%-> 51% does more for you than 0% -> 1%. The reason is the chance to be hit doesn't change proportionally (first case can be though of as an additional 2% miss while the second case is just 1%).
You may not have seen the new recommended Best in Slot gearlist for Death Knight tanks, but essentially it incorporates all the offset pieces with bonus armor in lieu of traditional avoidance stats. We can finally choose to gear almost entirely for effective health, sacrificing more avoidance to get there.
I honestly don't know if Blizzard realized what they were doing, but they basically ensured that none of the plate tanks will be using their T10 when they can get bonus armor pieces with vastly superior EH instead.
ICC- Bears in plate, throwing shields.
Well, you know how the cycle goes. In the beginning, EH is king for progression. Once you get the place on farm, a more normal rounded set becomes practical.
...well, actually, once you get the place on farm, you get your Tier set more so that you look well dressed and get a fun new toy in the 4 set bonus instead of actual survival stats because you don't need that kind of min/max anymore.
Stay strong. Stay smart. All heart.
On your second point, all my offset pieces look exactly the same as my set pieces. The 4pc bonus more than likely has a specific use, and by the time that use is realized, I should have the badges for that, after having farmed up the sexier offset pieces.
I think they're experimenting with making tanking more pro-active. They started by dropping the 30 minute cooldown on shieldwall. Giving other tanks more cooldowns. Not allowing us to chain pot (so they become mini-cooldowns).
And of course having DKs rely on cooldowns initially.
A fun set bonus that may give us a preview of how Cataclysm looks like? (once again they're trying to keep avoidance 'lower' in Cat, so it's going to look a lot like ICC I think).
I certainly hope they aren't trying to make every tank into a paper-bag with numerous tricks to keep themselves alive, and if they are bent on giving out more and more low-cooldown low-mitigation cds then they have some serious homework to do with the class that currently has them and under-performs the rest of the tanks in most settings.