Then whoever was online at said time would get it, free or contested
When bosses are up near start-end of primes, there is always pvp.
Players have the choice to organize themselves once in a while and log in out of their regular schedule. Look at baium, there are plenty of examples of alliances staying up late or waking up early to try and contest it. That is a reasonable compromise since the server is EU.
But its not possible to do it on a daily basis. And it ADDS UP FAST, especially in the case of bosses(since there are many), couple that with xp scrolls being much more accessible now and ou get the picture.
If anyone managed to lock down those bosses if they were not locked to EU prime and got all the advantages they bring, sure, kudos to them and they deserve the advantage they fought for. But locking it to EU prime is just giving free shit and it goes completely against what the game is meant to be.