What are the common general groups of kaic ratings of breakers? 10, 14, 18, 22, 25, 35, 42, 65,100, 200 kaic? It would be interesting to find out where the actual available fault current ends up to be after doing an actual fault current study comparing it the devices. That is how out of wack your systen really is.
If on considers 100% available fault current at the service entrance and then assumes that all the system must be 100% rated because there has been no coordination study done then at least you know what trouble you may be in. This would justify starting with the PO first to find out what the actual available fault current is from the POCO if you are still in deep dodo have a professional do a coordination study for you in order to pinpoint those devices that are definitely not rated for the actual available fault current.