Come to terms with the facts and the inconvenient truth for you.

The fact is that Rawr-Rawrs do get killed every time in EU as long as they don't spawn in late night or early morning.

And I want to kill him at 7-9 in the morning (he has been at these hours many times), why don't I have a chance?
RNG boss time spawn is total stupidity.

Because you didn't even try going at those times.  Just quit the lying already.

my man is really substituting reality lmao

Make it so that a boss chain can't spawn on two servers at the same time.  This includes the entire group of bosses.  So until bhed, rednose, dimtree die, it wont spawn elsewhere. 

No spawns on seasons.  

Potentially when they do spawn, have it be like world bosses where its anounced game-wide.  Ofc this will get annoying to people not interested so have it disableable in settings -> alerts

That means, the train would be forced and you wont have two kill groups making two seperate train.

You must be on a different EU to me because the boss trains for field bosses on EU are rammed normally as everyone is after feathers. I attend them regularly for that sole reason. You just have to use the boss discord to catch the correct server for the train and then it's off to the races. 

1. If you need to use discord, then the game has bad design.

2. What is 50 or 100 that fight these bosses vs 50,000 players that don't care about them at all, and the main reason is rng time spawn.

3. Only now, when there is an event, the number of people interested increases because this one seal is worth more than the entire drop from the boss.

4. Train bosses have always been toxic, some can cooperate, others cannot, some can wait, others cannot. Besides, since the field boss spawning system was changed (boss by boss), the train stopped making sense because there are even bigger conflicts, the train is divided into 2, sometimes even 3 trains, and there is even more confusion.

Conclusion: I am very satisfied with the planned change of field bosses to world bosses, and if they had fixed, specific spawning hours, I would immediately put my alts there.

Just can't admit defeat.

EDIT:
Actually, I changed my mind. I'm tired of hour-long field boss trains. I hate the idea of less chances of feathers, but I'm even more fed up with field bosses being nothing but damage sponges.