Looking at other games for examples: in the Metroid series, most monsters spawn once per room. They also sometimes drop health and ammo pickups. All the enemies in a room respawn every time the player enters the room. In the Metroid Prime series, enemies only respawn if the player has traveled at least two rooms away (when the room is dropped from memory).
I see two notable things in this example:
- Enemies only respawn at player-controlled times.
- There is an incentive for the player to kill basic enemies.
I'm not sure whether the "spawn once per room visit" setup would work for AVWW or not. It might be worth trying! The spawners wouldn't even need to be visible to the player or be destructible. This would give the player a sense of satisfaction as they clear out a room, and it would keep the room interesting if the player returns to it later. I can see maze rooms being much more enjoyable with this system, as the player would feel like he has really cleared out portions of the maze and made progress. It might be appropriate to make normal enemies a bit tougher with this system, as the player will have to deal with fewer of them. Having more spawners in each room would also be a possibility.
There would obvious be problems with boss fights... perhaps special spawners could be used in these rooms to provide a constant supply of enemies while the boss is alive and revert to normal spawners after it is defeated.
The other big issue I can think of is the tendency for enemies to pile up in pits and the bottom of the map, and to kill themselves off in water and and other hazards. Metroid solves this by having many enemies stand in one place until they notice the player, and by having some basic cliff-avoiding logic on the enemies that do move. I don't know how viable "don't walk off cliffs" AI is in AVWW's engine, but it could be a simple solution to the problem.
The high rates of health and ammo pickup makes enemies a bit more fun in these games, but it's not directly applicable to AVWW. The Metroid games don't have the health/magic potion system, so the player is more reliant on hunting down regular enemies to heal. AVWW doesn't seem to be trying for that kind of system, so the drop would have to be much less frequent, or not related to the properties that potions/scrolls affect. Frequent drops of something that the player would want a lot of could make fighting through hordes of basic enemies a lot more fun! Many games use XP in this way, but we don't want that here. Others have small amounts of currency drop from monsters, which also gives some meaning and progression to fighting the hordes. Maybe something like Consciousness Shards would be a good choice - it would give players a reason to get out and fight, but there wouldn't be a huge gain from farming. Making enemies only respawn when entering a room would also help prevent farming. Making higher-level enemies drop greater numbers of shards would encourage players to venture into more dangerous areas. This would certainly require a dramatic change in the quantities of shards required for various actions, and the existing shard drops found in dungeons would have to give more shards to still be worth something.
Whew! There's a lot of things to think about with this. From all of the complaints about enemy spawners, pesky enemies, players avoiding enemies, and so forth, it seems like this system might be in need of a serious rethinking and overhaul. Players are going to be spending most of their time fighting basic enemies - let's make it a fun as we can!
EDIT: My suggestion, in brief: Spawners should be invisible and indestructible. They spawn one monster each when the player enters the room. There may be more spawners in each room. Enemies do not respawn when killed. Boss rooms use special spawners that behave like normal spawners do now. Enemies are smart enough to avoid walking off of cliffs, and may be slightly stronger or have more health. Enemies drop small amounts of consciousness shards and occasional small health/magic pickups when killed.