While there is no strong "role" for classes in Diablo 3, you can't deny that each of them is especially good at something. The barbarian can receive a lot of damage (tank), the demon hunter can perform long range attacks (archer) and the witch doctor summons lots of minions (necro).
Wizards and monks purposes are less obvious to me. I thought that the wizard's main strength would be the ability to deal lots of damages (either with area damages spells, or simply with high damages spells). I've been playing Diablo 3 with two friends from the beginning, and their monk and demon hunter seem to kill mobs as fast as I do. Moreover, they have a far better vitality.
We have the same kind of stuff and the same level. I maxed my intelligence with the gems system; also I tried several sets of spells and runes. Am I missing something ?
Best Answer
The wizard needs some time to become really effective. A friend of mine complained about his wizard the same way you do until he hit lvl 25 and got the meteor skill.
The archon ability also boosts your damage tremendously while giving you a lot of sustain. Not to mention Teleport and the different armor types like ice armor and diamond skin which are powerful tools in the wizards's skill set to keep him/her alive while dishing out damage.
Try to experiment with different combinations and really use every rune at least once to know what your character is potentially capable of. If you find that the wizards is not working at all it might just not be your playstyle.