Re: your mute issue, make sure you’ve routed every instrument you have loaded into Vienna Ensemble to a separate output.
I agree that Finale-style “scrub playback” and being able to easily choose which instruments to hear based on the selection at the time of starting playback, like in Sibelius, are indeed excellent features, and I hope that both of these will eventually make their way into Dorico, though I cannot promise when it will be.