Most orchestral libraries (talking about the decent - good ones) are recorded in a film scoring stages using various mics (tree, OH, Close etc). Its important to remember that when using condensers in a big hall some low end usually accumulates do to the natural sound of the room or other artefacts. I usually cut everything under 30-40HZ on instruments such as violins, violas, woodwinds etc… It really seems to clean up clutter and make everything clearer. In regards to compression, I almost always soft compress my groups 
just feels right, no other justification for it.
Hope this helps!