"I also sense this largely was a protest vote...a throw the bums out....not really a 'we love the Dems and want to toss out the Republicans' vote."
Exactly. A lot of Republicans did not deserve to keep their seats, and the voters told them so. I think the rest of your sentence should read, "....and we'll do the same to YOU, too", for the Dems. If they screw up, the voters won't be patient with it for very long.
most of the losses occurred in areas where the Dems had previously held seats anyway most of the time.
In other words, they were just reverting back to their normal political situation.
It wasn't like there was a anti-GOP wave in the South or something losing tons of GOP seats there. We lost at least one or two there, but not a huge amount.
The one shock was KS-2 in my mind. But, we could gain that one back pretty easily.