Fair. As you said, I think the 4 party limit still allows a fair amount of variety in that regard. Those different roles can be filled by quite a varied amount of classes, for exemple the wizard "archetype" can be filled by both the wizard, the sorcerer, the warlock or even the druid with the right build. At the same time, you can play the same druid as a defensive fighter if you want to. Builds can be flexible enough to not having to be limited to one cookie cutter composition every time.