Not dopey at all. Do also remember that some instruments, even though they have been recorded in stereo, might be better loaded in as mono instruments. I am even finding that in the violin sections, particularly on the more "abrasive" (sorry - for want of a better word!) articulations, there are a couple of musicians off to the right being more enthusiastic about their sffz. Thus, when I have 2nd vlns panned 30% left, there are still major contributions from the right hand side of the stereo picture. I am experimenting with narrowing down the strings, whilst still maintaing stereo of some kind. Logic has a plugin which enables you to play around with the stereo width. Will report back with anything interesting.
The other thing to remember, is that when an ensemble is recorded all at the same time, each instruments' entire frequency ranges will be reacting with one another, interfering, masking etc. etc. To use pure instruments and mix them together in the computer can't recreate this subtle effect. When doing a pop mix, I routinely mix out the bottom end (within reason) from everything but bass drum and bass guitar. Especially electric and acoustic guitars - which sound gorgeous as solo instruments with full frequency reange - can ruin a mix with the amount of low frequency program material they provide.
I have started eq-ing individual instruments with good effect. Mostly subtractive, as it is often a part of the sound that is interfering that can stand to be attenuated. One opposite example is the trumpet sounds, where I do like a little extra sparkle in ff passages.
Have a good play, tweaking!