"Until Cataclysm".

I have been looking with hungry eyes at Icecrown tanking gear for my Death Knight. Now, I know that I resolved to be a DPS through and through on my Death Knight this time around, but I've found it quite enjoyable to itemise myself differently to other tanks. Namely, I love +armour items, so I've picked up all that I have access to, giving me a 2,352 boost to my armour; roughly a 3.2% boost to mitigation (from 62.42% to 64.46%, both numbers with Horn. None of those numbers are typos -- that's the way armour diminishes.)

Anyway, I was looking at these, which I'll very likely never get -- they cost 8 Primordial Saronite, after all. And I happened to scroll down to that particular comment I've linked to. I thought it would be good at this late stage of Wrath to remind everyone of what "Until Cataclysm" actually means in terms of upgrades.

When Wrath was launched, Ensidia, in their iLvl164 epics from Sunwell, went straight into Naxxramas and cleared it. They complained that it was too easy. It wasn't. It was intentional. The way that gear has been designed after TBC is that the uppermost tier should be usable in at least the first raid of the new expansion, in order not to result in "Green is the new Purple" syndrome which afflicted people in the transition from Vanilla to TBC.

Now, let's look at some numbers, just to point out that this is something we can extrapolate reasonably from existing data:
BT/Sunwell Epics: iLvl 151/159-164. WotLK Heroic Epics: iLvl 200
Icecrown Epics: iLvl 251/264/277. Cataclysm Heroic epics: iLvl 300. It would make sense from the pattern that Cataclysm epics will be 300.

So, why is it that iLvl 164/264/364 epics will be viable for content from which, pre-farming, you can pick up iLvl 200/300/400 epics? The answer to that is itemisation. Blizzard has said* throughout Wrath that items are not perfectly itemised with every stat you could possibly want straight from the first tier of raiding because it's boring when a new tier comes out and the only gear-picking you need to do is "Well, this one gives +5 SP/Haste/Crit/Int/Stam, so that's my upgrade!". This is why, though we are getting somewhat simplified stats in Cataclysm, we're also getting the option of "Reforging" items -- adjusting their stats slightly to get them slightly more in-line with whatever stat we will want to focus on (Most likely, for us, Intellect, since it'll give spellpower, of course... But we'll see!) -- this forces us to think about our gear if we want to min/max.

We have also seen blue posts saying that Icecrown gear is far more perfectly itemised than any previous tier, because it's built to last.* Again, let's look at previous evidence. This comparison is between the BiS-crafted Sunfire Robe of Sunwell and a Priest's Tier 7.200 robe. Because Spirit was nigh-useless to us in 3.0.8 (A mere 11% spellpower from spirit thanks to talent and glyph. Remember those days? 11%!), the Sunfire Robe destroys the Tier 7 -- you could re-gem Hit rating wherever you would like in order to make up for it: your Tier 6.5 gear would be competitive, if not better in slots such as these; at the very least it would enable you to get into Naxx.

So, certainly it is the case that those legs, and every other item of iLvl264, and some of 251, will be viable in the Plain of the Elements (Which I think is going to be the first raid, but it might not be. We'll see the order in which they choose to do them when they give us more info). "Until Cataclysm" isn't quite right, and it suggests that you'll be sharding all your purples a week before the expansion launches just to get some final gold sprees from the abyss crystals. Instead, Icecrown loot will be useful "Deep into the Cataclysm raid on Normal difficulty".

*All quotes are without their respective sources, because I don't want to spend ages trawling through MMO-Champion to find them. Just trust me that they exist, though.