Thanks all for replying to my post, you gave me enough material to play with in my mind.
In the mean time I was working on my game, and some things just became clear as I worked on it.
Like I said the game I'm working on is a bit unconventional because I experiment with the lack of a map, and space isn't there always as you expect it to be..... Anyway, I started giving monsters the property 'in sight' 'approaching' and 'within reach' as a description of their distance to the player, but even in this extreme alpha playtesting I find it annoying not to know how much feet the monster is really away, so I started displaying numbers for that :-)
It's a balance I now see, some parts in the design should maybe feel random until you played enough to know what the chances are ('checking the foliage for food, a berrybush gives food 90% of the time and there's a 4% chance of waking a sleeping snake' is information you don't want to spoil, it will become apparent (or not) to the player one day, and she can base her chances on it.)
Hitpoints, distance and attack (possibly after identification spell) are a must,even when it's only to give the player the feeling it can make a difference by planning her moves, playing tactics.
And then there's a big grey space in between where the developer decides. I see that in Brogue there isn't much to guess about the monster stats while in other games that's something you find out about while playing.
I would not like to make a game that's basically a spreadsheet even when it's a challenging spreadsheet, but I understand now that an adventure without clear stats will probably become a linear experience to the player where she doesn't feel what went wrong or what she could have done else in tactics, and therefore easily gets bored.
Sorry for my elaborate sentences and silly english.
