You're not going to see this, ever.
By design, Pandora lets you pick an artist you like, and plays enough of that artist to (hopefully) keep you listening, while inserting other artists into the stream that are similar in one way or another.
Their business model is to charge record labels to expose artists to listeners who haven't heard them, but are likely to enjoy their music (based on various similarities). The labels hope you'll go out and buy stuff from the new artists you're exposed to.
A stream with only one artist = no revenue for Pandora. Isn't going to happen, unless they went to a pure subscription business plan.