Monks - The second best tank in the game?

[Lhancelot]

I have a running discussion/debate with a pal of mine, and often times the monk class is brought up. We have a difference in opinion on the class, and I was curious to see if more experienced players would have more insight on this topic. My questions are as follows:

1. Are monks overpowered in a group setting?

2. Are monks capable of tanking, in fact are they considered the second best tanking class in the game in a group setting?

3. What group is more efficient? One with a warrior, sk, pally, or a monk tanking, and why?

I should mention the debate often revolves around how the monk is capable of doing three of the group roles, that being DPS, pulling, and tanking and how according to one of us in this debate no other classes can do so much, and do it so effectively.

Is it true? Are monks the ultra class that can nearly do it all AND do it great, or are they simply another dps cog in the group setting machinery with a penchant for pulling thanks to FD?