Nah, I don't see a problem.

Like Yoshi said, there's more than one way to approach the dungeon. I see groups whose goal is the end boss, and I see groups who go in there to grind through the trash mobs for SP. They would have to increase the time limit if they forced you to fight through all the mobs to get to the end, and I for one like the 60 minute time limit. You have to know what you're doing before you enter.