I too have noticed the ridiculous amount of spam coming through Disqus lately and the various issues with it, so here's the deal thus far:
1. I've set comments to require approval before anything with links in it get posted. Necessary evil.
2. Blogger has essentially locked out anyone but Facebook from doing external comment syncing at this point. I'm grandfathered in because I set up Disqus back in 2012 when I created this version of the blog, but if I ever delete Disqus then I pretty much lose all the comments forever and I'd have to go with either Google's built-in commenting system or Facebook comments. So for as troublesome as Disqus has been, there's not many viable alternatives.
3. I can't afford to switch back to Wordpress, so don't even ask. The blog is too popular and server costs would far exceed what I make on it.
Basically, it's vitally important to keep flagging spam comments as spam when they pop up, because then Disqus will auto-delete them and learn. I went through the dashboard and found another 40 or so spambots tonight that hadn't been flagged. If it's spam, click on the little drop-down box on the right side of the comment and Mark As Spam! It'll notify me and that way I can mass-delete anything from the spambot.
Hope this helps.