The other problem is that there are far more instances where having a speed boost saves your life (or everyone else around you) rather than instances where being immune to snares or roots saves your life.
But the nail in the coffin is that frost mages wouldn't be able to root us. Other classes not being able to do so would be fine, but Blizzard won't let something bad happen to a mage. Those players correctly chose the "I win at everything" button at character creation. I'm actually surprised mages haven't been given a reverse GG, something that pushes all enemies 30 yards away from them and roots them for 15 seconds on a 15 sec CD.