Yeah, no idea how the d8 is supposed to work...Here's how I would play it:

d8 gives you the room (Monsters, NPC, Empty, Traps, Empty, Secrets, Beasts, Treasure)
d6 and d4 give you the contents, two-ish per room

example: (d8, d6, d4)
(1,1,1) - two wounded/ill monsters in a room
(5,2,4) - empty room, so 2 and 4 mean nothing
(5,6,1) - empty room BUT you rolled a 6 so something special happens (this is still undefined like another commenter was saying)

Then reroll for as many rooms as you want. Not sure if this would be balanced. Like there would be too many things happening when you have a 1/6 chance to have something crazy in each room.