Two million doesn't sound like a lot compared to the viewership ratings of yore, but relatively speaking it's still "second most-watched for BBC One" of the day. I'm not even sure the consolidated ratings will give a clear picture of how many watches Doctor Who at this point, because some will hold off until they can binge the season...
But of course, this will give fans (and haters) fodder for fantasy ~~football~~ franchise management, while Disney (whose ratings remain a black box) mull over their decision to renew the distribution deal or not.