Melee, especially warriors, can keep going long after that wizard is oom, and they can break up their damage into big and little pieces as well as move while doing damage. Wizards are stationary, with non-granular attacks, and a finite resource pool from which to inflict them. And those crits are pretty rare.
Only rogues and berserkers should be on par with wizards, but warriors and probably monks/beastlords are. some of that is berserk, some of that is procs, some of that is how many buffs there are for melee vs. casters.
The buff thing is an issue I've brought up on live and in other games as well. The way melee is handled is so complex with lots of variables to adjust, and a lot of gear to adjust those variables. Magic is very frequently a retardedly simple system with a single mechanic for both avoidance and mitigation (resist check), and few factors that increase damage. So melee can invest time developing themselves through itemization. Magic users can usually only increase the depth of their resource pool, a limitation melee don't even have to begin with. Endurance is pretty much a joke even on live, but there are a ton of focus effects for casters there at least.
