I fully agree that a high geared player can be a massive noob and a lower geared level that knows what he is doing can play better. But there must be some kind of gear measure. Let's say the first dungeon needs you tube level 10 and you apply for a party, but another player joins and he is also level 10 with level 4-5 gear and he got to level 10 by killing chickens (it's an example :) ), you just won't have enough power to clear the dungeon no matter that the guy knows his spells well, they won't have the firepower needed.
But yeah if your gear has, let's say, 100 score and the dungeon needs 70, you can party up with a bit lower score players.
Hmmm i agree with your example.But then the dungeon must offers higher level gear than it's requirements.Not like in many rpg games - the dungeon requires minimum level 10 gear and the boss there offers level 9 gear :D
Regards