If you want to deal a lot of damage and at the same time not have the ability to take more than two hits from something/someone without dying, then be a wizard. Wizards do more damage than any other class in this game thus far. Archers are second in damage dealing, and they can actually take hits! Clerics have very few harmful spells so most people who have clerics don't bother fighting, they just heal and buff. The summoner is all melee, but you can summon spirits, either healers or fighters, to help you. I hear that people become bored of warriors and knights easily because they don't have many interesting casting skills. Melee's can be annoying because you constantly have to chase something that runs to attack one of your party members, so you're not doing a lot of the attacking. Paladins are also melee but they've got some nice skills.

Hope that helps a little bit more.