May I join in on this thread, please, having read every post carefully twice over the summer and autumn, during which time I've completed a string quartet using Sibelius 8 and the Solo Strings packs?
I can see that I have the same concerns as you, David; and that my work sounds uncannily similar to your files, Paul (thanks for posting!).
So much so that - just as, say, Janet Baker's voice or the Amadeus' string sound are recognized immediately for their timbres or textures - the VSL/Sibelius sound is unmistakable.
This isn't a bad thing. And I'd say we have to be realistic about what a notation program like Sibelius (and eventually Dorico) can do.
I think I'd settle for knowing that I can, though, consistently produce the best possible.
And both Andi and the documentation (especially v. 3.2 of the 'Optimizing Sibelius Playback with Vienna Ensemble' pdf) are both helpful, of course!
But there are indeed so many combinations of so many variables in the patches and presets etc that even something simple - perhaps in binary tree form to help make the necessary either/or decisions and eleminate wrong turnings - for, say, solo strings would be a great help. Also some way of knowing which tweaks are additive and which cancel one another out, and/or changing which settings achieves nothing without some other parameter's being altered first.
Similarly a list of changes to experiment with - but one that put each parameter in order of likely effectiveness… "x will make the biggest change because it does y" and "don't expect to hear greater realism with a until you've balanced b and c" etc!
For instance, I find the violins have a thinner - and often noticeably 'whinier' - sound than the cello (which is invariably excellent); and that the viola - because it's a quieter instrument, perhaps (?) - tends to sound growly in its lower register, and insipid above C.
I do believe all this is only a good starting point; and would really welcome specific/concrete guidance… I know the samples are capable of great sound.