Even with my new headlight unites, they still fog up a little in the corners with the conditions are right. I've tried to adjust the vents on the back side and it still fogs up from time to time.No, it is not normal.
One cause can be the vents on the back of the light housings. There are 3 vent tubes coming out of the back of the housing. There are small filter screens on the ends of the tubes, and small caps that go on. There is a tendency for the caps to get pressed on too snugly. Recommended fix is to remove and reseat, just until they reach a small detent. It is possible to press them on too far.
Another reported problem is a bad seal between the housing and the front lens. The seal is just a silicon sealant. The dealers would replace the whole housing. Guys often fix their own - stick the housing in an oven at low temp to soften the sealant, pry it apart, clean off the old sealant, apply fresh sealant, and put back together.
Normally the easiest thing to do is take it to the dealer, who will likely just replace the whole unit.
When I put 55watt HIDs in my 2014 Sport, I would still get the condensation/fogging.When I pulled the headlights out of my rebel one week after I purchased it new last fall to install the HID kit, I made sure all if my vents were open. And so far I have not seen any moisture in the housings at all. Maybe the HID's heat is burning any moisture off since I have them on when I am driving.