Anti-Skid does exactly what its name states. It keeps the tires from skidding. All wheel speeds are monitored. If one has a wheel speed less that the others, it would be treated as a skid and the hydraulic pressure to that brake is reduced (or stopped) until the wheel speeds back up.
Pilots still apply brake pressure as they see fit. The Anti-Skid works without any input from them at all. On a 767 there is no Anti-Skid switch in the cockpit. It's always on.
If the aircraft has Auto-Brakes, it does everything and (not a good idea) the pilots wouldn't have to have their feet on the peddles at all.
Is it possible for the performance of the anti-skid system to degrade over time, and is there a means by which its functionality can be continuously monitored?
No. If maintenance does their job right. There’s no degradation, only failures of components. Once the fault has been identified and repaired, the system is 100% functional.
If things are failing, you get flat and blown tires.
Could factors such as contamination, corrosion, or physical damage to the wheel speed sensors; faulty or degraded wiring and electrical connections; overheating of the anti-skid control unit; contaminated hydraulic fluid; sticking anti-skid control valves; uneven or worn brake components; or a sticking brake actuator contribute to the degradation of the anti-skid system—and might such degradation be inferred through the analysis of tyre wear patterns?
As previously stated, either the system works or it doesn't.
If you're wearing tires unevenly.... it doesn't work.
The Fault Isolation Manual should be consulted as to what area might be causing you problems.
Any one of the areas you listed could be causing issues.
The "BIT" or Built In Test on the front of the unit would be the first place to go.
