Huh, I actually thought I was pretty close to the end of the main game with basically those places I mentioned left (unless there's a bunch of stuff behind the Demon Ruins since I have avoided it like the plague)
I think I'll play around in the DLC a bit longer but if it gets too frustrating I'll bail out. It's a bit hard to tell right now because there's literally only been 3 enemy types so far. Sanctuary Guardian (who while he roughed me up a bit, as I noted is actually a very simple boss once you recognize his patterns), the... plant dudes who are very easy, and then those stone dudes who shouldn't be that hard but I kept being bad and they're very punishing if you do mess up. (oh right and now that i think about it a few dogs in the lower section before the dragon.) I mean, based on the Royal Wood I'd say I seem to be okay for this place so far, but we'll see if/how it escalates.
Each of the gates is a full area. As someone said, lord vessel is kind of the middle point not counting dlc.