For what it’s worth, I’ve tried, for the first 10 levels or so: the Warrior, Engineer, Ranger, Necromancer and Elementalist.
I’d say the Warrior is the easiest to play so far, owns to survivability, and that the Elementalist is the hardest. The others are somewhere in between.
I’ve decide to level the Warrior first and put off the others until I better get the hang of GW2.