You can always 'enter element picker mode'. With a little practice/knowledge you can block that element/frame/etc. forever. And/or add a layer with Privacy Badger and block altogether most of the sus domains.

Another 'trick' I employ (always with Firefox) is that I open links not to a "New Tab", but instead I use "Open in Reader View" add-on, so I "Open in Reader View" (it does exactly what it says on the tin), so I only get the clean text and the relevant images. That works for almost every website.

You should go and report that to whoever maintains your block list. The information on where to report ads is at the top of the file, and you can find the file itself in ublock origin's settings. Better yet, create a rule and submit it along with the issue, although people who maintain lists for long periods of time tend to be much better at it and might not find your attempt useful. I do it anyway to show some respect, they deserve it.

Good tip, I'll try and do that in the future.

Is there a best practice for developing rules that match randomized class names? There's a web app I use daily at work with obnoxious upselling banners that always come back if the page is refreshed and it's the only place I've run into this annoyance so far.