Having a computer that is quite slow, this is a problem for the loading pages too, and not only at boss battles. Most of the times when exiting a dungeon or switching to another map i can hear the music of it, the sounds of mobs, even players fighting if there is some close by, but i am still stuck at a loading screen filling slowly. That is to say it seems i am already on the field on the server side while i am watching the loading screen on the client side. If someone where to lure a mob near the entrance during this time, i surely would be killed without being able to do anything.
It seems to apply to loadings followed immediatly by a cut scene too. For example in the first cut scene, based on some videos i have been watching (like here :
http://www.youtube.com/watch?v=oI2m2map_5o ), you are supposed to see :
1 : Lady Shizuka running ;
2 : a close up on Tiamat ;
3 : Lady Shizuka saying "give it back" ;
4 : and then the rest of the cut scene.
Well on my comp i never see the 1 and 2, i begin directly at 3... Because when 1 and 2 are played, i am still stuck at the loading screen.
I am pretty sure that i have heard the caracteristic sound being played when a boss is first introduced and his artwork displayed when i was still stuck at a loading screen too.
So the problem is basically to spawn the players on the server side once all loading screens and cutscenes are finished on the client side, and not spawn them before that. And to wait for loading screens to be finished before lauching cut scenes. Because at the moment all that is launched without checking if the players are really ready for it.