lol I'm none the wiser Worto .. I guess the thing that is causing confusion here is that during the stars phase you can earn bonus stars for each individual kill that you make during a game (I think this is still the case?). So individual kills are awarded on some level (which is great), I don't know if their Elo is taken into account at that stage (but the general rule seems to be that you can earn more stars and more elo in 4ways).
It still kinda looks to me like maybe the 4way competition should be separate from the 1v1 competition (separate leader-boards), I really don't know though... If any info about how it's calculated does come to light it would be interesting to work out once and for all if there's any advantage in competing in 4way games only as opposed to 1v1 games only.
One issue I have with the system as a whole is it seems to throw up some unusual results, it's probably a fairly accurate system though. My perception of how it all works is probably inaccurate, I don't know what it's like now but sometimes players with superior win records (and win rates) were finishing below players with inferior records, also it seemed possible to beat someone 3 or 4 times (or more) and still finish below them..
Elo is probably the only viable system for the format but the thing I don't particularly understand about it is (and this is just my uneducated observation) you can gradually take chunks of Elo off of someone by beating them a few times, but they pretty much only need to beat you once to take it all back again (almost cancelling out your head to head record - because the earlier victories gave you higher Elo and them lower Elo, you were then the bigger scalp to take when you met again later and lost)
...therefore it seems like even if you have a 3-1 or 4-1 record over a player (a fairly comprehensive record in your favour), you can both pretty much have similar Elo ratings, they may even have a higher rating than you if they have played more games over the season.