that is a very good addon, especially for warior tanks, I often see how wariors easily lose aggro, their aggro forming ability sets aren't done very well, low level tanking isn't much of an issue though, like tatsu said, unless the healer starts making problems about it then it's fine, as long as healer is not the target it's all good, hell, I was tanking as a rogue for 5 levels, up until level 40 you don't really need to worry about losing aggro too much, Zul Farrak is the place where good tanks can have a blast of fun though, if you have an imba healer you can constantly add mobs to your aggro count

Paladins are quite the tanks gotta say, mine is lvl 75, I have a DK tank 85 lvl heroic geared, funny how my hp is only higher than mages hp due to blood presence

(and gems/enchants) blizz didn't really thought this out, I mean, plate and cloth most of the time have exactly the same stamina, difference is only power stats, i'm healing on my shaman in my DPS gear without any problems or worries about mana, the game really needs a balance update, at least for specc/stat, if not for power balance.