I have recently bought Descent (the core-box) and me and my friends have have played the game about 6 times now.
So far i must say it is an awsome game (i didn't not expect anything less of it), and i'm having loads of fun playing the OL (and besides that it seems the rest of the group likes to play heroes more anyways).
After the 2nd game the heroes found out that they can very effectively shut rune-doors behind them, locking themselves into a room so no monsters can get in behind them, and they come out when the room is cleared. And after that they shut the door again.
This means i can't spawn anything in that room anymore (i CAN, but there is no use as unnamed monsters can't open rune-doors, right?).
I have the feeling these rune-doors in combination with the line of sight makes it extremely difficult to get monsters on the map, and after that close to the heroes to have any effect.
Am i missing something here, or is this just one of the hard parts being OL?