A quick way for SR staff to confirm that this is the problem, is to create a new .onion address pointing to the same port as the original one. This will use a different set of introduction nodes, and as the address will not be made public, the attacker will not DDoS those introduction nodes. If they can access the site with this new .onion address, then it is definitely the introduction nodes being DDoSed. Keep in mind sometimes it takes a little bit to access a newly created / launched hidden service though.