2. They are WAAAAAAAAY to heavily penalized for ranged weapons. Common, 10 times penalty with no access to spells? Farmer can shoot arrows better than duelist? Somehow this doesn't seem right. Killing some monsters in melee later on in the game is a real pain in the rear even if you can make 2,5 hits in a turn... i.e. Emperor Lich or Ancient Chaos Wyrm come to my mind.
Well, duelists do get the concentration skill, so they're not completely hopeless casters in the late game. By the endgame, they're plenty strong enough to tank almost any powerful creature without fear anyway--their damage output probably exceeds any class except maybe archers. The missile penalty is severe, but it doesn't mean you can't use missiles at all--it just means you suck with them compared to other classes. Missile ranks aren't so very important in the grand scheme of things; I've finished lots of characters with <6 ranks in missiles.
All in all the class bore me pretty quickly
I'm not surprised that they bored you quickly if you completely ignored all of the stuff that makes them interesting! It's like playing a non-casting wizard or a non-missile archer.
Overall, I'd consider duelists among their easier melee classes to play. Probably on par with monks or beastfighters (who play quite similarly).
Hoping to win with every class, doomed. Archer, Barbarian, Bard, Beastfighter, Druid, Elementalist, Farmer, Fighter, Monk, and ULE Priest down.