To keep this from being voted as a duplicate of this, let me clarify. The other question asks for DM tactics to battle chokepoints. Its answers are all focused on fighting at these choke-points. I ask for ways to avoid PCs creating/using choke-points. I want my PCs to jump into the boss room which I've designed, and explore it during the match. I want them to enter rooms and not stand in the corridors during the entire dungeon.
Many classic dungeon maps are modular corridors and rooms, where PCs are expected to gradually progress through. Examples include the Doomvault, Tomb of Horrors, or the Forge of Fury. Advanced DMs can bring a stronger sense of an actual lair filled with enemies, when they start mixing enemies from multiple rooms, but mostly the books describe each room independently, and as far as I've experienced, unless something makes a particularly strong noise, fights are usually contained to the enemies in each separate room.
Now, as both a player and as a DM, I've experienced the choke-point strategy. Boss rooms are a prime example, but this works in many situations. Players are faced against the next room, riddled with enemies. The DM reads their campaign book,
Yeah, you have 4 undead zombies, 2 living suits of armor, and a weakened Lich looking at you once you open the door. Roll initiative!
Ok, so PCs at the door, a long corridor behind them, and enemies within the room. The frontliners now simply stand in front of the doorway (effectively blocking it) and the nukers blast from behind and drop massive AoEs on the room while enemies do their best to
- break the front-line
- teleport / run-away with some hidden exit
- spam the party with AoE back
- attack the backliners with ranged attacks suffering from cover issues (thanks to the frontliners)
(This literally happened in my last session. The Bard dropped his Storm Sphere in the room, Druid dropped a Moonbeam, and while the Lich teleported out and tried his best to mess the party up, all the minions inside the room died while slightly bothering our Cleric.)
With specific enemies, breaking the party is somewhat easy. If you have on-going AoEs, if you can teleport, if you can protect yourself from the party's on-going spells. But most often, your group of enemies are just a bunch of martial enemies, and they have no way of splitting up the party.
As you can see from the maps, rooms are usually very different. They have platforms, and pillars, and parts with difficult terrain, and this all should be something for the party to take advantage of. But its so much easier to just use the doorway as a choke-point, that rooms are basically just used after everything is dead, when searching for loot.
How can I incentivize my players to enter rooms and take strategic advantage of each room's layout, when using the door as a choke-point is such an easy and effective strategy in many published adventures? Specifically, I want players to want to enter rooms and fight there, not just stand at the doors.
When I design dungeons/enemies from scratch, there are some ways of handling this. However, when using official content, it's gets harder to adapt the environment or enemies, and still keep true to the written content. We don't play in AL, but for example, we're doing Tales of the Yawning Portal, so strategies that also work in such published and mapped out dungeons are preferable.