It's a step forward that rancho is at least voting more than one account.
No solution will ever be perfect, but AS's has been the the best suggestion so far. I believe a trial was actually done in the early days of Steem and it looked promising when it came to distributing the coin among others more. I hadn't thought before reading you post that it could help in this situation too, though.
Yes, a note about why a dv was done would certainly help.
Recently I was trying to calm someone who regularly earns decent reward for their posts and had a rancho vote (not a regular occurrence there and this was only one of three) trimmed, so they didn't really need to kick up the fuss they did. UVM usually only gets a few dollars per post, however, so I would have said a trim wasn't really necessary in her case and can see her point more.
As I said, though, it would be preferable not to have to trim in this way in the first place. Cap the mv amount and the rewards have to be spread further anyway.