Greetings Garry!
If I may, I would like to share my user experience related to the issues you have sounded.
- You mention a slow movement, with several section involved. I tend to think that perf-leg is not reflecting that particular situation, if you apply its underlying principle to the desired effect. In real strings, you are not suppose to "hear" the finger movement, neither it happens as fast as perf-leg suggests it should be. Sus vib patch sounds natural with the slow, mostly bowed action, hence the vibrato diferrence - its a new, less stressed bow versus transitioned, "inside the phrase" note of a perf-leg. I mostly use combination of the two, and perf-leg reserved only to those moments which cry for "one bow direction, finger movement".
- When I get to mixing DS, I cannot but notice the difference between its initiall sound and Chamber (only other VSL section I own). And in my mind, I try to portray a strategy, which would close the gap between mixed mics recording, and 24 personal mics, which is DS is about, in real life engineering terms. I always sence than Mir is not enough to fill that gap, and try to act as a real mixer would do with personal mic tracks, be it in EQ department, additional effects or whatever.
In large, I relate to your concerns, but eventually I find them rather natural for this technology, and a minor trade-off for some invaluable benefits it brings along.