THeck, how many DMs lost their first party to a kobold running scared into the cave and telling Irontooth that there was a group of shiny new PCs to murder?
Or have had the players massacre the kobolds leaving one to tell Iron Tooth all his minions are dead and the mean bastards are coming for them.
Personally I think the dungeons are much too static and the guard-setup is lacking a LOT. The PC's usually defeats a dungeon in many separate encounters. Realistically they should have been slaughtered by a throng of monsters. Not much fun for the players though.
This is one of the reasons I really hate dungeon crawling - most of it makes little to no sense at all.
My own modules are outdoors 90% of the time and if the characters attack a lair, they KNOW they are gonna attack the whole damn thing. The monsters are going to come at them in waves until they retreat, get killed or slaughter the monsters.
This way the players are going to think of game in logical therms, not meta-game "we will get encounters that suit our level". The players have to think of way for the characters to subdivide the problem into manageable encounters.
The problem with this "logical" approach is that I have usually only made the problem, not the solution, so if I have passive players they either just walk away or walk into a deathtrap.
BTW, one way of handling big dynamic encounters is as mentioned above, to allow the players a new use of second wind and/or regain their encounter powers. I would rather have it by the players slamming a door in the face of the monsters, doing some great AoE control thing that makes the monsters back away or similar action. This means I have something between no-rest and a short rest. A little breather?
4e has something else to handle big dynamic encounters too, it's called daily powers.
Oh, and one thing, - I really hate consumables like healing potions. I feel they can take the edge out of bad encounters and make them bland. Or, the DM just has to pile on even more




to make the encounter hard.