I've been thinking about what to do about these but I don't have any great answers beyond what is being done.

I do think the $25 cap is too high. Even without any overvoting, $25 will show up pretty high on trending some days. I would reduce it to $5 or $10 and make more posts per day.

Ultimately a big part of the issue here is that Trending is misnamed. It should really be called "Most Voted" in which case no one would be surprised that these show up, right?

As for curation, the curation algorithm is designed to address this automatically. Repeated high value posts that get high votes (whether it is these or just a consistently popular author) will attract earlier and earlier votes which return more of their Trending rewards to the reward pool. Burnpost gets most of its votes between 1 and 3 minutes which means 40-80% of curation is returned to the reward. Voters get something, which is fair IMO because they are consuming their valuable vote power, but they don't get anywhere near as much as they would get doing actual curation (more effort).