like Hedgerow Hall, there's nothing you're "supposed to do" except what you want your character to do.
The most fundamental rule of gamer philosophy is that a game has any form of combat or direct head-to-head competition at all, it most certainly does have something you're "supposed to do". I would advise taking very great pains to make combat as dangerous, risky, and demanding as it possibly could be made. A very heavily fighting-oriented character who runs up to a random player on the street and attacks should not have a 50-50 chance of killing them, accomplishing anything that could be considered "winning", or even of surviving... the odds should be quite a bit lower than that.
[EDIT] Oh yeah, as to the "four categories of players"... I think the "Explorer" category is often taken much too literally. The essay on the subject that was linked to a couple of weeks ago dealt with "explorer" type players in a much more general sense, focusing on experimentation and gathering of knowledge rather than physically exploring a map. By nature, this sort of game holds a lot for such players.
There wasn't MANY players, but the ones that were playing were absolutely addicted to it, spending more hours on the game then a junkie for EQ does.