Pickling a hero at start screen is gonna be interesting. Picking a hero based on its 'class' abilities would be a very bad call IMO, and here is why:
1. Of primary importance will be hero selection based on DMG type (ranged vs melee). Since every hero can only have 2 weapon loadouts, this is probably the single most limiting factor when it comes to character creation.
2. The thing of secondary importance will be the mix of character skill 'types' available to each hero. For example, a cleric having 2 defensive skill slots, 1 movement, and 1 utility.
3. Armour type, and the ability mods associated with that type come next, as this is also static for the hero you have chosen.
So, the only REAL customization comes from hero (character) abilities. But you have to ask yourself, why do they seem so chill and laissez faire about balance issues? Ill tell you why - because the character skills, within their various types, are going to be almost totally homogeneous. Sure, a wizard will have a blink ability to keep it mobile, but it will be almost identical to the warrior's leap, and the ranger's ground slide or whatever. Who cares which one you pick? They are basically the same skill with different animations...
Prove me wrong Sony.