Our DDoS mitigation techniques don't involve IP blocking at all, since we operate a Tor HS and relying on IP blocking to stop attacks there is not possible. We use same techniques to protect our clearnet infrastructure, also because DDoS attacks we get come from Tor exit IP ranges and we don't block Tor IPs just to stop these attacks, unlike many other services do.
I can't go in details publicly on what we do exactly because we get DDoS attacks almost everyday by someone who reads this thread and they could use this information to bypass our protection. I say this with a full confidence because we had a very powerful DDoS targeting our systems some minutes after posting the Lightning Network announcement.
Interesting.
If this technique you use is so good maybe we could use something similar for bitcointalk forum, if that can handle forum traffic.
I know several people have been looking for good cloudflare alternative, and I think that even theymos is not trilled with using cloudflare.
Please open a ticket or write an email at support@exch[at]cx to resolve reachability issues. We won't leave anyone without a proper resolution.
I will let him know, this is probably something on his end.
Thanks for quick reply.