With HIDs the likelihood of glare increases with condensation so they may fail that in future.
One way of removing humidity is to remove the bulb and insert a pipe connected to a vacuum cleaner, It will cause the air to be changed and replaced with whatever is surrounding the unit. Poke the pipe into one of the further recesses and it should create turbulence that will flush the whole unit. That won't really help unless the source of water ingress is located and fixed though.
Headlamps in particular pump air in and out as they are powered-on then powered-off. So if they are sitting in a pool of water, or water is sitting in a seam that leaks, it will be sucked in as the air in the unit cools.
I was amazed when I found that my Discovery had vent tubes in the loom to the low-level fog lamps that presumably dip into rivers etc. when on off-road trips. This allowed them to breath without taking in water (theoretically).
It has nothing to do with it being HID's, the defraction of light as a result of condensation affecting the beam pattern is the same for both the lense based Halogen filament lamps and the lense based HID lamps.
But they're super-sensitive when it's HIDs 'cos everyone gets dazzled good and proper.
They are no more sensitive than halogen filamnet lamps......a light source is a light source and the light emmitted obeys the same scattering and defraction laws of pyhsics.
The trouble with HID's are they are a bit like Marmite, you either love them or hate them (the same happened when Halogens lamps were first introduced in the 70's).
THE bigest issue is poor headlight aim (which is part of an MOT test clearly) and poorly aligned headlights of any type will dazzle others.
Granted a HID setup produces more light (although the major percentage of this is used to illuminate the ground creating a more consistent illumination).
Its just the lates thing of blaming HID's when in reality its not specific to HIDs
