It wasn't just that the NS10s had weak lows, they actually had about a 5dB bump in the mids.
Anyway, while I find the attitude that if you fix the mids you fix the mix to be a bit simplistic - I mean, you still have to get the rest right also, they can be the most troublesome area for many people.
Don't scoop anything. You're throwing out a lot of the good with the bad when you do that, and you'll wind up with a mix that'll be lacking much of it's backbone.
The mids run - as stated - from about 1k to about 6k, give-or-take, but typically the real problem frequencies come in around 3k-5k. But don't just attack those assuming anything. As said, you gotta use your ears. Scooping = death.
The good ol'
parametric sweep works wonders here. Run it on your individual tracks before summing them together and you'll likely avoid much of your typical "mids problems" from the get-go. Add to that some judicious differential EQing (taking 2 or 3 dB away from this track at this frequency while adding a couple of dB to that track at the same frequency in order to give them each a tonal balance that fits like a jigsaw puzzle) and you'll be three-quarters of the way home before you even mixdown. Then on the 2mix, if the mids still seem a bit honky sounding, a final parametric sweep on the 2mix should take you the rest of the way.
P.S. this takes knowing your monitors, too. People who liked the NS10s (I was never one of them, myself) tended to be folks who needed the boosted midrange they gave to expose the mids. You gotta know your speakers and know how the mids translate on them to know that you're getting the mids truly right, and not just right-sounding on those speakers.
G.