Plus, it seems to me that scarcity of resources + infinitely respawning enemies is an even bigger recipe for hording than more intermittent hard enemies would be. Why use bullets if you can just run past stuff or use the wrench? Especially since enemies will respawn anyway in a few minutes, which completely removes any justification for using your valuable resources on them. This doesn't encourage doling out resources in small doses it just encourages not using them at all if you don't have to. I discovered invisibility fairly late in this game, but once I got it I rarely used bullets again.
And invisibility's actually a kind of good argument for my general thesis that this game is a case of great ideas with piss poor implementation. It's a neat idea in concept...."a skill that makes you invisibile!" but rather than using it as part of some greater stealth system, instead it just quite literally makes you invisibile. Which means not only that it's overpowered to the point of being game breaking, but also it's just not that fun to use because there's absolutely no skill involved in it. You just push a button, turn invisible, and run past enemies. If I remember correctly, you don't even have to decloak to first to become invisible again, so as long as you have enough psi juice you can just remain invisible indefinitely if you want (only decloaking to attack things). Not that I'll complain about it much, though, as quite frankly, invisibility is the only thing that made the Rickenbaker and the Womb level tolerable for me.