It may be common, but it is not acceptable for a brand new car. It is not part of the design and is a defect in the construction of the lights. They should be water tight sealed from the factory. Push at the dealer if you have to. Try to get a few photos as evidence since chances are good they will not have water when you want to bring it to show them. They better be bending over backwards to help you out. Dealerships don't really make much money on selling cars. They make money in the shop. This is their prime opportunity to convince you that you need to come back to them for all your service needs. If they make too much of a hassle, take your future business elsewhere.
Welcome to LGT.com. Enjoy your Legacy. I sure do love mine.