Yes, they can spawn from the round stair wells. Usually the spawn piles for draugr and skeletons are found in an areas with rocks around it in the swamp, and inside the crypts. You can usually snipe those with arrows, but keep an eye on the aggro. (One of my favorite ways of dying in the swamp is to stand there for too long thinking that one more arrow should do it, while the draugrs and elites close in.)