I guess I'll just never understand this. On the rare occasions the lows are too much, I just roll them off a hair and it's perrrrfect. As far as the highs are concerned, I must have some hearing loss up there 'cause I boost the dooky out the highs with the tweet at noon on my UL410S1 just to get the upper mids and highs to poke out of the mix a little!!!

YMMV
Depends on the bass. I like an almost Marcus Miller tone (not that over the top, but plenty of grind, sizzle and big low end), and have my tweeter at about 10 o'clock and never,ever, ever boost treble on the amp or preamp with any of the Markbass stuff. However, I use relatively aggressive J basses with always new stainless steel roundwounds.
Regarding dialing back bass... it's not the amount of bass to me, but the nature of the low end. Yes, I can keep the bass flat or slightly attenuated on the SD800 and punch up the low mids a touch, but that's not the same thing as using that head flat through a more low mid voiced cab. The probability of a shelving bass control and a fixed Q semi-parametric mid control exactly 'fixing' a voicing issue is pretty low.
That being said, it all sounds darn good, but I continue to find that some combinations sound better than others. Again, on this site, we split hairs a touch. I can get my tone through just about any full range cab and SS head. However, some stuff just sings to me!
That being said, one of my least favorite combinations is the SD800 and the 401UL (I). If you have that combination, that might explain your rather extreme EQ to end up with some articulation. Those two pieces of gear have their holes and peaks lined up exactly with each other to my ear. Just IMO... it surely doesn't sound horrible to me at all, but is my least favorite of any combination I own. The LMII with the 410UL (I)... ahhh.. that's what I'm talkin' about!
Edit: Of course, one man's least favorite is another man's favorite! That's what makes this all so cool!