Hi @bonkerz,
The spam comment filtering is all handled by Disqus in the same way when using this plugin or the official plugin. So I believe you must be experiencing a higher rate of spam coincidentally at the same time as switching plugins. However the support team at Disqus might be able to give more information as to where the spam is coming from, as they have more visibility on that.
Edit: I just realised I misread your question and it was in fact relating to the WordPress comments system rather than Disqus. It sounds like those comments might be coming from xmlrpc spam bots perhaps. If so, signing up to Cloudflare (note below) will help with that. I’d recommend that as a first step to try.
One thing which may help is to connect your site to Cloudflare. They have a free plan which should help to reduce spam comments and also boost general site security too.