I've been doing level design for a Metroidvania type game. Up top is one of my old designs, and below that is a much newer map. Here are a few things I've learned over the years:
- Centralized locations (big rooms that connect to lots of other tributary paths) are a good thing. From these points the player can launch expeditions into your smaller, more dangerous, locations; and feel like they can return somewhere afterwards.
- Tributary paths should not continue forever and/or randomly connect to other tributaries. The player will lose any sense of placement in your overall design and randomly wander your world with no sense of progress.
- The only time you end up with too many rooms is when you run out of unique ideas for those rooms. After that, don't bother adding anything else.
- Compact maps are better. On an aesthetic just-looking-at-a-bunch-of-rectangles level of thinking, they're better.