I think the attack was itself a response to a doxxing attempt. Also, archive.is being a free service doesn't quite fit with claiming they are malicious. The overall picture seems still positive.
If, when I visit your site, your site causes my browser to participate in a DDoS attack without my knowledge, your site is malicious.
Works for me. I use only Tor so it is actually far more accessible. Archive.is uses Google's Recaptcha, which for some reason rejects valid solutions submitted via Tor.