Not really crazy considering some of the encounters in the current end game.

A lot of them are so dependant on insanely good aggro management, raiding them without threatmeters is near impossible. So many of the boss encounters need the tank at the top of the threat, and then 1 or two more tanks at the 2nd and 3rd position so they become the target after a certain spell/ability/aggro drop whatever.

Bear in mind Blizz are releasing another 25 man instance thats harder than BT at some point before the next expansion (read; the next Naxx... awesome instance, most players never seen much of it if any as it's now obsolete), lord knows what kind of threat management is needed for the bosses in there.