A comment from last post involving sandboxes and NPCs got me thinking about how an encounter from our last game session would have required such a different approach in our 4E days.
The Old School Approach
Last game, the characters were trudging overland in the Joten Mountains. On the hex map, I have a key with the major lairs, ruins, and strongholds, but I make liberal use of the random encounters in the Cook Expert book for D&D. The guys are currently a mix of 2nd and 3rd level characters.
The party descended into a shallow valley; from somewhere down the length of the valley was coming a noisome stench of decay - a cave mouth. Emerging over the far side of the ridge was a large troll; it saw the group, howled a war cry, and came bounding and snarling down the side of the valley to where the characters were taking a momentary rest.
The players had 2 rounds to respond while the troll hurtled towards them; the fighters formed a defensive wall while a few of the shooters tried peppering the troll with arrows. The magic user cast invisibility on the thief, who snuck to a vantage point where he'd have a backstab attempt once the troll went past him.
When the troll engaged the front line, the thief stepped in and scored a 20 on his backstab, maxed his sword damage, and killed the troll with one epic thrust. The table erupted in cheers.
The characters were almost surprised by the second troll coming out of the cave lair behind them, but the thief was looking that way and alerted the others. Thinking quickly, the magic user blasted it with his wand of paralysis, and the troll missed the save. They quickly doused the bodies with oil and started a fire.
The 4E Approach
First off, a basic Troll is a 9th level monster, and 2nd and 3rd level characters shouldn't be facing one; level appropriate challenges for an encounter should be in the N to N+4 range, where N is the character level . The main issue is that armor class, attack, and damage all scales in 4E, so once the monsters get too far ahead of the party, they become unhittable and too damaging.
Of course, if the DM picked a Troll encounter, they could always scale the Troll down a few levels so it would be level-appropriate for the party. One or two trolls wouldn't be enough for an encounter - a 4E encounter would be a mix of monsters covering different monster roles, such as brute, leader, controller, artillery. (Trolls are brutes). Or the troll could be beefed up to be what's called a "solo"- a single monster tough enough to take on a character group without support.
Much of this is hypothetical - 4E doesn't have or use any wandering monster tables or random encounters whatsoever. None. If I wanted to orchestrate a Troll encounter during our 4E days, I would've planned it in advance, built a challenging and interesting level-appropriate encounter with a mix of monster roles (brutes, soldiers, artillery, leaders, etc) and I would've introduced this as a faux-random encounter at a time of my choosing.
Wow - I'm sitting here re-reading how different the two experiences are from the DM's perspective.
In the old school approach, I have no idea what the party could meet out on the road. Fights could be easy, they could be tough. A pair of trolls for 2nd and 3rd level characters seems on the tough side. The game emerges for the DM at run-time just as it does for the players. Who knows what will happen? That is very, very entertaining.
When running 4E, the encounters were pre-planned, and the difficulty level was pre-set - I almost always knew how an encounter would go.
I don't recall seeing this particular distinction - that the randomness inherent in older game systems keeps the game just as fresh and unknown to the DM as it does to the players.
So here's to random encounters, reaction rolls, morale rolls, and treasure generated on the fly!