[I've moved the discussion to this poll, as it more accurately captures the thoughts expressed so far.]
Simple question, I suppose.
For several years now, the insistence on having two tanks in every raid has felt overly contrived. Too many encounters essentially throw in a tank-swap, and not a lot else, which is becoming a less tenable reason to have to gear and maintain two (or more) tanks for every raid guild and/or group. Because all of the tanks are now largely identical in their capabilities, there appears to be even less reason to ensure that two are in every group.
Look at Hellfire Citadel:
Where are the mechanics that necessitate two tanks other than bland swaps?
And if we removed the need for a permanent second tank, what mechanics could be put in instead?
Think about it like this - imagine that guild groups only used a single tank, but there was a requirement every few encounters for another. Could the role of the Demonology warlock or Enhancement shaman be reviewed, given their utility toolkits? Could Retribution paladins, Frost death knights or Arms warriors fill in when required? Could the mechanics such as cleaves, saber lashes or stacking debuffs that necessitate two tanks be rethought altogether? Could adds streaming be CC'd or kited rather than just rounded up and melted?
It's also worth noting that due to gear-sharing amongst specs, it's now never been easier to shelve the constant second tank in favour of more interesting mechanics.
So, what do you think? Votes in the usual way.