I agree. I really dislike Investigation and would like to see it removed. Easy enough to house rule however. If a PC is investigating a scene, I want to hear what is it he's trying to do. "I investigate" is just as meaningless as "I handle an animal" or "I survive"
I feel like you're trying to infer how the game works by looking at the character sheet rather than reading the rules. In the "Using Ability Scores" chapter, it lays out fairly specifically how the various Intelligence-based skills differ.
History, Nature, and Religion represent the ability to recall specific information from these respective spheres of knowledge.
Investigate, on the other hand, is for researching new information, making a deduction based on clues already found, or drawing inferences about the physical world based on general knowledge (as in the example of the weak point in the tunnel).
I personally think it's a reasonable fallback for when the players are presented with a puzzle none of them can crack. At the very least, a success on an Investigate check should earn them a hint or two. There's nothing wrong with playing a character who's smarter than the player, and this is a good way to emulate that.
It's all well and good to require your players to describe how they are using a skill; in fact, that's how you're supposed to do it. House ruling a skill out of the game because you're afraid players will use it as a crutch -- that's just cutting off your nose to spite your face.
Investigate is a good skill, and there's a very clear need for it in the list. It's up to the DM to make sure it's used wisely.