The skill specifies oozes, aberrations, caverns and spelunking, but that is not the entire field of study. It is called knowledge: dungeoneering.
What we must ask is: what is dungeoneering? It is the act of dungeon delving. So, a character with this skill should be knowledgeable about things you'd find in a dungeon as well as things you'd do to go through a dungeon.
An important thing to note, however, is that this is a knowledge skill, not an active skill like use rope, survival or spellcraft. It gives you 'book learning', not 'practical use' information. Thus, you would know all about what you can do it a dungeon, but you need other skills to know how to do those things. As an example, you know all about what needs to be done to fight an ooze creature, but you may not have the necessary skills or abilities to actually do what needs to be done. Another example, you might know that people delving deep into an underground lair often need to repel down cliffs, but you would not know how to repel unless you had the proper climb skill (or whatever skill the DM uses for this action).
One question that needs to be answered: What is a dungeon? Caves and caverns are specified, but what else might qualify? People typically refer to old subterranean ruins as dungeons. What do these different areas have in common? They are covered areas that are not occupied by a civilized society. That seems to be a pretty good definition.
Things that might be covered:
1.) Historical dungeon delvers (overlaps with knowledge: history).
2.) Famous dungeons (overlaps with knowledge: history).
3.) What devices are useful in a dungeon (but not necessarily how to use them).
4.) The types of traps that people use in a dungeon (but not how to detect them, exactly what will be found, or how to disable them. "The Kravel Priests were known to favor magical traps that created fire. It would not surprise you if there were some magical fire traps in their ruins.")
5.) What types of beats are known to 'settle' in old ruins in a certain area (this won't give you a list of creatures in the dungeon, but could be used to help eliminate possibilities or confirm which of a few possibilities might make more sense - this overlaps survival to an extent).
Using the skill for these areas keeps it useful and interesting without even coming close to making it overpowered. I hope you find my approach useful.