I did understand what you stated originally, and maybe you could fool me :) no dis intended.
I also just realized that you said "there's almost no audiable". I just found your statement "it's a waste of time" rather bold, and didn't entirely agree. I guess it also depends on the library as you say, and maybe even more, how much reverb you smear on it. One thing to say about dynamic samples is that you hear the direction in the playing, which is what often lacks in sample library based music. For example a crescendo patch with strings you hear the vibrato grow much more naturally then if you would have done it with velocity crossfade.
And of course I agree that this is much more audible with solo instruments then with ensemble patches. But you could also argue that as soon as you have two instruments playing together, like unison flute and clarinet, they are already an ensemble(!?), but I would still argue that if you can make some magic with dynamic samples you'll get a much more human performance... But if it's worth the trouble, is up to the individual.