re: the attack damage outputs, I see the different weapons as encouraging different playstyles/roles in a team or even solo.
With my Mesmer, if I go Scepter and offhand, it's pew-pew time on single targets and quick generation of duplicates.
If I go Greatsword (and an illusionist using a 2H sword is awesome), it's all about engaging multiple targets simultaneously and having some serious damn damage output.
If my Guardian uses a Mace, he's tanky and gets lots of defensive shields. If he goes Sword, it's much more offensive-minded. Shield offhand gives me, obviously, shield options. Torch offhand lets me set myself on fire for an area DoT, or breath fire for a cone DoT/cone cleanse on allies.
I am seriously digging the idea of having different roles (offensive, defensive, buffer, debuffer, crowd controller, healer, etc.) be swappable and embodied as weapon choices. Champions Online has a similar mechanic where you can switch between offensive, defensive and utility at the click of a button (and even change costumes with it). It's a way of making sure that you don't spend three hours yelling "LF HEALER!". Anybody can be a healer, they just need to switch gear. Anybody can be a tank, they just need to switch gear. Obviously, characters who ARE Guardians or Warriors will make a more effective tank than say, a Mesmer using a staff. But all in all it still makes for a flexible system overall.
It's definitely a different paradigm than the old days where a warrior was a warrior was a warrior and would only ever be good as a meatshield.