Never taken DOM + LSD, but I have combined DOC and LSD a few times (to me, DOC is superior in every way to DOM, but they're similar drugs, as you might imagine, definitely brothers). It's a good combo for sure, though I didn't find any particular synergy. It seemed like the DOC was the primary drug, and it was colored by LSD's nature, making it a bit more out there mentally, and more visual.
Adding a 4-sub tryptamine (I particularly liked adding 4-HO-MiPT) to DOC, however, made for an incredible trip that was greater than the sum of its parts.