The bosses from the world map were not like the bosses found in dungeons. In terms of rarity, world bosses were a lot more valuable than dungeon bosses.
Everyone could encounter the dungeon bosses as long as they enter the dungeon, but world bosses were extremely hard to encounter.
Most of the world bosses' CD (cooldown) only happened once every 3 to 5 days, and the most ridiculous ones took a whole month to cooldown. Every time it was available, the players would fight tooth and nail to get to it.
World bosses did not belong to any one player, so everyone could fight it. However, whether or not you actually got to fight depended solely on the player's true abilities within the game.
Holy Pure Eh's team of knights had been fighting the Violent Ape King for the past few days, and they had finally brought its HP down to 5% when suddenly the Century Flower Guild appeared and killed them all, stealing away their boss.