Any tank is a good boxing tank these days, but I'd still recommend a Paladin.
They are the least maintenance, or put another way - least clicking necessary.

Most people who run heroics play the tank as the active toon, with the others as support for the tank.

Another option would be the DK tank, because you can start them at 55th and they're almost as easy as the Pally.
Warrior or a Feral Druid would work as well as the DK or the Pally, if you prefer either of those classes.
I personally like the pally most, because they're a mana user like all the dps in your party, so totems will synergize the most.