Blizzard blatently lied about the tank shortage. Basically they said it's because they are insulted in LFR.
Let me tell you : its bullshit. As always Blizzard lies and you know why ? Cause the shortage of tanks is due to the horrible redesign of their role at the hands of the catastrophic "ghostcrawler". Myself I used to play tank since classic wow, but MoP killed that role for me. It has become SO boring and SO useless (you have nothing to do during the raid, NO skill involved) that I stopped playing it.
There are no tanks cause tanking has become brainless. Bring back skill to that role. Let us see what is a skilled tank and what is a bad tank (no difference as of today) and people will play that class again.
Enough of blizzard lies. Shortage is because they destroyed that role, not because of lfr abuse