No, I am not an expert with Altiverb at all. But I did use individual track convolution for each and every instrument once (about 16 instances). I rendered each track separately with reverb, and only then mixed them. It sounded startingly better than one where I used a more normal premix (strings, woodwinds, brass, and percussion totalling four instances). It didn't sound muddy, but sounded much more real and full. I reasoned that this is because when you hear an orchestra live, you are actually hearing each of the those instruments producing their own reverb separately, and then that is "mixed" in your ears as you sit in the building. So it is analogous to the individual track convolution approach. You are NOT hearing a dry "wall of sound" (a premix) that then reverberates. So I guessed that this method might be superior to the usual dry premix approach.
I can see that nobody else here does this. Perhaps because it takes longer to do than the usual premix approach which I admit is much more convenient.
I have been too lazy to do that A/B comparison, but will try to and post something.