I think the main issue with melee is the huge spread of builds that can come with them, and in general the heavier reliance on itemization, when it is a finite and randomized resource.
As an example, you can be a dual wield fighter who uses one handed weapons, and end up with only one handed weapons that give bonus to one handed rather than one handed and dual wield, along with the possibility of the weapon having a bonus to strength, or finesse, which are generally two mutually exclusive attributes as well as getting melee weapon of a type that nobody in the party is specced to use.
Meanwhile magic users only really have to worry about intelligence and memory more or less and will almost always get items that work for them in every situation through the random generation.
Armor choice is also straightforward, as there does not appear to be much of an incentive to use only medium or light armor over heavy armor for melee types, and magic users can just stick to anything that gives magic bonuses.
