Tanking in 5 mans should be easy for sure. Tanking in 5 man heroics should be engaging at the very least - not boring.

Tanking in LFR should be easy too (though honestly the queue in there is the longest for tanks and making encounters more interesting to tank wouldn't affect LFR tank population too badly, it may actually help streamline queue times).

But like Paul says, tanking in raids should have a difficulty progression from the first boss to the last.

I love tanking, I am sure there are many other tanks like me who play 2 - 4 tanking classes. Making tanking extremely easy may encourage players who have never tanked before to give it a go but it does nothing for retaining tanks who already love their role. I did a full clear of DS10 on my bear and have not queued again for DS on it. Just no desire to tank. The same for my warrior. So now I go and arena or bg instead because for me tanking this tier is supremely yawn inspiring.

And if I want to raid, I go and heal or dps instead as there is something beyond mindlessly spamming my "rotation" in those roles. Tanking needs to be engaging. Hopefully the active tanking model in MoP will add some stuff for us to do, but the issue will be the same - if a bad tank gets splattered and only good tanks survive, then either the difficulty will be such that only good tanks succeed or it will be such that everyone succeeds and the seasoned tanks get bored.

I don't envy Blizzard this balancing act. I just think they need to make raid tanking more challenging. The tank shortage has always been at the 5 man level, not at the raid level.