I'm a bit disappointed that High Rock is so small a lot of places had to be left off the map. I'm not suggesting it should be the same size it was in Daggerfall, that would be absurd and not at all practical without a procedurally generated map, but it would be nice if it was a bit bigger. But I think the only difference between getting it in the base game or getting it in an expansion is that we didn't have to wait as long for the base game areas.
Similarly I don't like how Valenwood is presented, it doesn't look anything like the descriptions in the various in-game books. It's too open, too many clearly marked (even paved) roads and too many permanent, stone cities. But again that wouldn't be fixed by leaving a chunk of it out of the base game only to add in later. A lot of people have pointed out that much of Summerset doesn't fit the descriptions we've been given either.