.I am going to respectfully disagree with one thing jojo said. That is that he shouldn't be tanking what he is tanking. In comparison to what a normal tank can tank (in my case, a pally tanks for us), he takes 1/3 the dmg that I do.... if that. While a mob will hit me for 1100, it will only hit him for around 300. That is a big difference in tanking ability and shows that an "off tank" monk is nothing more than someone that might be able to tank for a couple of seconds in a group situation, where you have 4 - 5 dot mobs (sometimes multiple mobs), in the current state, we are no tank... or off tank for that matter.
From a healer point of view I will have to partially disagree with you. Defensive Fighters are much better tanks than monks due to their mitigation. However, as Jojo stated they are not necessary at all in group situations. A mob will hit you for almost full damage but you can avoid 3/4 his attacks completely. Avoidance tanking is partially unreliable becuase of a chance of big spike damage, but in Jojo's case she only dies maybe once every few days from a nasty round of bad luck on avoidance.
Just lastnight Jojo was tanking level 50-53 mobs. Some pulls were 4dots in groups of 3, some were 5dots in groups of 2(and often getting a roaming add mid fight) She was even able to tank 2 6dot lvl 52s at once. Note this was also Rahz Inkur where crowd control is disabled. From my experiences I can say for sure that Monks(Drunken at least?) Are capable of tanking high end mobs for longer than a few seconds. She has done it for 30 lvls
(dont nerf my mUnk pls, but if you do make sure she is doing the damage an offensive fighter should)