Here's Yuuki Aoi rehearsing for and then voicing a TV ad for a new light novel called Chronicle Legion, from Shueisha's "Dash X" label.
She apparently reads 330 characters in 30 seconds -- eleven characters a second. Many of these are probably single syllables and some double or more.
Ao-chan has great vocal skill. I think she's a good actress, too, but her powerful vocal equipment and control are what really set her apart.