The dudes in Shadow Labs still do the old Intimidating Shout. Nearby party members are feared, but the tank is incapacitated. When the tank is gouged, blinded or incapacitated like this, the mob does indeed charge off after the next highest threat - a perfect example of this is the Moroes fight - If you have seen one tank get blinded and the other gouged at the same time, then you have probably seen a healer in deep trouble :)
In this particular case which still exists in Shadow Labs, (unlike regular fears now), a lucky taunt can indeed keep the mob on you (Growl does force the target to attack you for 3 secs - check the description of the skill here and on Wowhead). The downside to this though is that if you don't get lucky, you have used your growl and after you regain control of your toon, you can't go and taunt the mob of the healer/DPS - for this reason, I think it much wiser to save the growl for when it is really needed.
It is also a good idea to have the whole party stay close to the mob as if someone is out of range of the fear, they seem to be the ones that get targeted by the mob.