Actually i feel it's good to put those world bosses in those maps where not many people go.
Dragon spine is awesome, so if some players can discover it at the same time, then all the better.
Now of course, AoC engine is still demanding, even more with massive crowds, but that's something we all bought with AoC, which is not a modern MMO with cheap and easy graphics.
Just tune everything down, any half decent computer these days surely can handle such load.