Besides the servers being bottlenecked there are fewer monsters and channels as you level up. This should be increased fast as the fun of the game completely dies out after a certain level.
Let me share my experience with you. Today I hit level 50, and I was very excited going for my first dungeon, it proved to be difficult and actually rather fun because of this. After doing it twice I was level 60, and I returned to normal questing, with a warrior who can pull all mobs together. This is so extremely easy for us, that I can sit down and rest by the fire while my mate tanks all the monsters in screen (20-30 monsters). While it’s okay that he can tank it, you should really increase the number of monsters in every zone past 60 dramatically. With more people reaching this stage it will eventually become impossible to do any quests at all. Not to mention increasing the monsters would increase the fun, as it’s quiet fun destryoing large packs of monsters, but actually irritating running around killing 1-2 with your entire combo and mana pool.
