A surgical EQ is sometimes a help, but not always necessary especially if things are tracked carefully. It takes a lot of foresight and wide gear selection (mics, preamps, instruments) to guide things along enough in tracking, where you know from experience how they will ultimately fit into the mix. Generally I find that there a few 'hot spots' that I come back to on instruments in general...usually cuts in the 350hz-600hz range on kick, guitar amps and toms (this seems consistent across good rooms, and a variety of quality monitoring systems). But this is the sound I like to hear, and it doesn't require much, maybe a couple of db. That's a subjective call and would still be fine if left alone.
Most surgery that I do is done on vocalists who have an unbalance in the frequency curve of their voice, mostly they are "green" beginners in their first couple of years of singing. There is always some kind of strange rise in the 1-4k range that is hard on the ears (i.e. nails on the chalkboard) that I never hear in more experienced people. About the only thing that would fix it would be to use a ribbon like an R84, but that can present other problems, like increased proximity effect at close quarters or possible damage to the ribbon by people who don't know what they are doing in front of the mic. I'd rather just notch out a couple of db's if it's otherwise fine and use a condenser.