Never mind rain - wait till you tow in the dark, the lights tend to reflect back right into your face! All Baileys are the same as well as several other makers.
One solution would be to swap the position with the front reflectors - re-wiring hasle though - remove the bulbs or slap some Duck tape over them which is what I do when towing at night.
Good point about the design though, van designers obviously don't test their products at night and why have you never read a bad review about the problem in a Van Mag test?