The consolidated errata does list the few items which are considered common. Everything else by default is uncommon. IIRC all rares are new items, but honestly I haven't looked at that list in a while. You can pretty much assume everything is uncommon and if you want a specific item to be easily craftable then make it common in your game. That works pretty well and honestly I suspect that is the general way this whole thing is working. I don't think they ever intended to go through and systematically rank every item. Most would be uncommon anyway. The main purpose is served, allowing the DM to manage item availability.