1.6.2.5 How do you intend to make a game that is challenging but not overly tedious?
Challenge should also be fun. One of Sigil's tenets is 'the path of least resistance should also be the path to the most fun'. What this means is that players shouldn't encounter an intersection where fun is to the right, but the more efficient route to character advancement is to the left. Ideally, they should be one and the same.
It's also a balancing act. Certainly not everyone will agree as to how challenging an MMOG should be. But there are already quite a few MMOGs out there to play. Some are easier than others, and some are more difficult. Generally, if you enjoyed the challenge level of EverQuest and its first couple of expansions, you will likely enjoy Vanguard as well. But, just as importantly, those areas most people found overly tedious (boat rides with nothing to do, or camping hours in one spot) will be addressed with newer, better game mechanics.