There are some simple things you can consider without taking away something the character has invested a lot of resources into.
We need to look at the text of the ability to really see what its limits are:
Wandering Eye (6 psi; conc., 1 hr.). As an action, you create a psychic sensor within 60 feet of you. The sensor lasts until your concentration ends. The sensor is invisible and hovers in the air. You mentally receive visual information from it, which has normal vision and darkvision with a range of 60 feet. The sensor can look in all directions. As an action, you can move the sensor up to 30 feet in any direction. There is no limit to how far away from you the eye can move, but it can’t enter another plane of existence. A solid barrier blocks the eye’s movement, but the eye can pass through an opening as small as 1 inch in diameter.
Phasing Eye (7 psi; conc., 1 hr.). As Wandering Eye above, except the eye can move through solid objects but can’t end its movement in one. If it does so, the effect immediately ends.
Speed of mapping and exploring
The eye, as written lasts for an hour and can travel at 30ft per round. That speed is equivalent to 300ft per minute. So, travelling at breakneck speed and not spending any time to look in detail at any room or hallway, it can cover an impressive 18,000 ft in an hour. Some of this will be spent back tracking to account for dead ends and going into rooms. If we lowball it and say 10% of the movement is spent backtracking. That gives the party an effective mapping capability of 16,200 ft of dungeon floor space.
Now we need to ask you some questions:
- Does your dungeon level have more than 16,200 ft of floor space? (Note I'm not talking about floor area, I'm talking about travel distance)
- Do your dungeons always connect in a circuit? (for example one level may have two unconnected sides that branch from the entryway, this would drastically increase the amount of backtracking required)
- Does your dungeon have random dead end passages that go nowhere? (Even after a seemingly long corridor moving with purpose in a particular direction)
- Does your dungeon have secret rooms and traps?
If your party wants to examine features of the dungeon through the eye, they will cut their speed even further. At a minimum they will be moving at a slow pace (move 15-30ft, pause to look around and examine details).
Traps, ambushes and secrets
The eye is not a creature, and it is incorporeal, so it won't be able to set off traps just by moving past them.
The eye only has darkvision and normal vision. This means it won't automatically spot secret doors, traps or hidden creatures.
The gloomstalker ranger has an ability they get at 3rd level which is relevant here:
You are also adept at evading creatures that rely on darkvision. While in darkness, you are invisible to any creature that relies on darkvision to see you in that darkness.
So the eye won't see any gloomstalker rangers or monsters with similar abilities.
The eye has no way to interact with the environment other than trying to go through solid objects.
Traps can be placed in any surface, including the roof and walls. Finding is going to be difficult for the eye, unless your party is spending time trying to send the eye through every roof, wall and floor, in which case the eye is travelling significantly slower in the forward direction than it's stated 30ft per round. It's hard to make an adjustment for this, but in a dungeon with 10 ft wide and high corridors checking in this way would easily cut its speed to one quarter speed, or further (depending on how thorough they want to be) just by moving around each square in each direction.
If they try to do a thorough search in this way for traps and secret doors, they run the risk of ending the eyes movement in a solid block of stone, at which point the effect immediately ends.
Sure the party will get an idea of where the enemies were at some point during their hour long search, but enemies can move in the same way PCs can.
In your prep for the session, position the monsters in different rooms at different times of day, that way you can move some (but not all) of them to a prearranged place other than where they were originally spotted. Also explicitly have wandering monsters that roam the dungeon.
Things that block divination magic
Unfortunately the Wandering and Phasing Eye are psionic forms of magic as opposed to divination magic. As a result magical effects which block divination magic won't affect the eyes.
The fact these powers are designated as magic does, however, mean that for the purposes of effects like antimagic field, and dispel magic they are (or can be) affected.