The Diablo 3 Monk is one of the classes in Diablo 3. It is a hybrid class as it is able to do damage like all Diablo 3 classes but it can also heal and buff. I have not noticed any other classes being capable of significant group healing, whereas the Monk has a very powerful group heal in its Spiritual Light ability.
Before you think the Monk is a healing class like in a typical MMORPG, you should understand what Diablo 3 is like. Diablo 3 is very fast paced. When you use your spell it is an instant cast to heal your group almost to full HP. It is not like you are standing there forever waiting to heal up your teammates. This ability is likely to make the Monk very good in PvP.
As far as its soloing ability goes, the Monk has pros and cons. It does do very well because it has good healing and good defensive abilities. This makes it very effective against boss type enemies. The real problem of the Monk class is that it does not really have any good abilities to use against multiple enemies. It has a few abilities, but they do not really compare to the Barbarian’s Cleave ability or the Wizard’s Electrocute ability. Both of these abilities allow the latter classes to rip through trash mobs and be able to get access to a lot of fast experience points.
I really find that this puts the Monk at an advantage for boss farming, but a bit of a disadvantage for farming regular enemies. It is hard to say which will actually be better to do. For example, the best way to get items for awhile in Diablo 2 was to farm enemies in the secret cow level, where players had to take down hordes of weak enemies. A Monk would be bad at something like this. On the other hand, taking down the Uber Diablo enemy also was good to farm once it was introduced into the game. The Monk would be very good at taking down an enemy like this.
There is still a lot more to be seen on whether or not the Monk will pan out as a great farming class. I can already tell you it will be solid in PvP.