Maybe they should just have quality affect durability and mod slots, but leave the damage the same values? Otherwise if they want to go the full random route, then go the full random route and have cool descriptions for the items, like crummy items could be "made in china pickaxe" and durable items could be "military grade shovel" and top notch items could be "professional grade" and then add other descriptive modifies like "destructive" for block damage and "sturdy" for durability. Go full looter rpg instead of this half assed approach.