My question is they going to increase level scaling for enemies?
I hope that Dawnguard is for high-level players personally. It just doesn't seem right to have Ice Giants, Gargoyles and Vampyr Lords be scaled, and thus killable by a level 2 character.
That'd probably just fall under Archery, since crossbows are just another type of bow. Just like swords, maces, axes, etc. fall under One-Handed.
Specifically, I think Crossbows are going to function like "Dagger Bows" in that they have special exceptions to their damage formula. They may have higher DPS, but they probably won't benefit from either/or the Overdraw Perk for bows, or Archery Damage enchantments, similar to how Daggers do not gain bonuses from One-handed gear.