Having played both games, I gotta say while DRG does have hordes, they're not on the same level as HD2. HD2 is the first game in a while that truly has made me feel overwhelmed by the amount of enemies thrown at me and I love it. In HD2 I even find myself doing stealth a lot to sneak past patrols.

Overall though I don't think it's worth it trying to compare DRG to HD2. They might look similar in some aspects. But they are vastly different in gameplay, experience, and mechanics. It's apples to tomatoes, sure they're both technically red fruits, but that's where the similarity ends.