Honestly, I think the Ellen is as good a choice as they could have made. No, she doesn't have singing experience, but I think they're looking for someone to step into the "nice mom" role that Paula played. Between Randy and Kara's incoherent babbling and Simon's too-on-the-nose snarkiness, they need to keep the puppies and rainbows in there somewhere.
I think that she, more than the Babbling Twins, will be a good judge of an overall performance. Which is pretty much what Paula did.
*sigh* I'm going to miss Paula.