Yes, precisely: they needed a living, flesh and blood person. The dead have earned their rest, and either way they're more vulnerable to demons than a soul still attached to its body. It couldn't be an angel because an angel wouldn't have been able to volunteer for the mission - they lack free will.

[Yeah, it's weird. Weird enough that Enoch is still unpacking parts of it even here, when it's all over.

...Might it entertain House, though, if it's so bizarre and complex? He'll keep going.]

...I didn't realize the extent of this at first, honestly. I had no idea why I was the only one coming forward.