Who cares about how they'd fare in the old system when that's not the one that would determine the outcome?
I'm surprised that you don't get the concept of average ranking. The average ranking does not give us any clue whether a song ended up in a country's Top 10, it's only overall. If you end up 11th place in every ranking, you'd still have 0 points. However if you end up 10th once but last in every other vote you'd still beat the other country. Since we don't know the individual ranking from every country, the ranking just gives you a big picture of how a song was doing but it's impossible to determine the actual place.