I had a look at the phoenix event discussion from last year and while there is a image of someone with 2 sets of 3 fully evolved birds i couldn't see any sign of someone with more than that.
But that is not surprising as they didn't ever announce that you could get more than 1 of them, and from what people calculated it would have cost hundreads if not thousands to get just the 2nd set of birds let alone to get them all of them fully upgraded. So for someone to have got 4 they would have been spending massive amounts of money.
To get just second set they had to get 27 artefacts which would mean 54 grand prizes so for a third set that is doubled, so 108 grand prizes probbaly around 50,000 essence,