Seeing as different judges are going to be appointed to judge different matches, it is definitely not certain that that 8-0 means that the other 30+ members share the same sentiment.
Another thing, this is Totallympics, I'm not expecting an 8-0 on any single match even if someone sends a 60 second clip of an Austrian mountain goat yodelling.
If people are going to change their votes in favour of an underdog story rather than what they believe to be a better song, then that is mostly a problem of the person and not the system.
Lastly, to make it a bit easier on the host and participants, the users could provide a ranking for the group stage, ranking 1-8 the entrants of group A, B, C and D. I think that four separate smaller rankings would be a lot easier and more reasonable than comitting to a 1-32 ranking
It also wouldn't give away everything to the host as well until the quarterfinal round starts.