Yeah, I once talked with a Tankadin who specced 20/31/0 for the same reason. In any event, I rolled a Warrior this time around to see what life is like tanking with a rage bar.
I started tanking dungeons as paladin and after some time it worked really well. People added me and invited me again if they needed a tank.
But honestly after I rolled a warrior I found tanking much more exciting. You have more abilities, a rotation and have to switch between stances (for Mocking Blow and Berserker Rage).
An example: Taunt is not only a emergency spell but together with Concussion Blow can be used in your rotation. Taunt, Concussion Blow, Taunt on main target, so it is kept away from the group without you having to put threat (and waste rage) on it. Meanwhile you can build up threat on other targets using Shield Slam and Revenge when available and Sunder Armor when those are on CD. Your damage dealers can start nuking the main target right away. You have to keep track of the time to come back to the main target to keep it on you (when the time of Taunt and Concussion Blow is running out). I loved doing this because it really needed my attention.
And because your abilities to gain initial threat on all targets, Blood Rage and Battle Shout, aren't doing any damage, it's way easier for people to use CC.
And another big plus is that you actually have a lot of gear to choose from. Together with the 10% damage reduction from Defensive Stance and the more specialized gear you are way tougher than Paladins. And you have to worry about running out of mana on longer fights. As long as you get heals everything is fine.
Gameplay felt much more satisfying to me, but also more demanding. I tanked all the dungeons as Holy paladin. And it got boring after some time. I basically just needed to pull with Holy Shock, broke LoS of casters so I got them to run to me, used Consecration and in the end of the fight Seal of Wisdom to regain some mana. Always worked like a charm, but not very exciting though.
