How many tanks are needed in 3.0

[Worldie]

You are doing Sunwell at least.

[dmok]

Just to get you a idea, we killed Illidan today with the warrior using crafted gear (270ish FR, 490 def) and the paladin with partially badge gear (220 FR, 495 def).

The warrior did actually die due to graphic lag (well, i told him to set graphic to non-existant but he forgot ) then i taunted the flame at 20%, and tanked it for 20-30 seconds with 70 FR (aura)... did i mention <3 bubblewall?
Anyway, just get 200ish FR unbuffed on the 2 tanks and they'll be fine with healers just constantly spamming max ranks.

This makes me very, very happy inside. Thanks a ton worldie.

[Consecrate]

You don't need a warrior tank.

You need however 3 tanks for most TBC encounters. You cannot possibly do Council and Illidan with 2.

Well, you can, it's like hard as hell, but you can.

If your DPS is good, you can kill shahraz with 0 SR atm.

Worldie darling, you can tank both the priest and rogue, I have been doing this for the last 3 months and it's not a problem at all really, just tank the rogue with the priest. It's funtimes, and your fuzzybear can go pretend to DPS if you have one!

[Worldie]

You don't need a warrior tank.

You need however 3 tanks for most TBC encounters. You cannot possibly do Council and Illidan with 2.

Well, you can, it's like hard as hell, but you can.

If your DPS is good, you can kill shahraz with 0 SR atm.

Worldie darling, you can tank both the priest and rogue, I have been doing this for the last 3 months and it's not a problem at all really, just tank the rogue with the priest. It's funtimes, and your fuzzybear can go pretend to DPS if you have one!

That's a creative way to do it, but you'd be a lot better off with 2 different tanks, so one can care for interrupting priest while the other bothers with the rogue.
That's expecially true if it's a progression kill, the OP was asking about that, not overfarmed content, i can probably solotank Council if i want but i'm not telling him to do it.