DELL-REF-MIB reports that dellLanExtension isn't defined but I'm including Dell-Vendor-MIB which does define it and that seems to parse correctly.
MIBs source is contained in Release 6.2.7.2-mibs within this firmware ZIP (http://downloads.dell.com/FOLDER03447532M/1/N3000v6.2.7.2a10.zip). Sorry, that's just how they package it seems.
I've successfully compiled dellref.my (renamed to DELL-REF-MIB.txt) by including Dell_ITA.Rev_1_1.my as well (renamed to Dell-Vendor-MIB.txt)
Name change is optional (except .txt extension).
I was including all MIBs in that package, how did you fix it? When I replace the ones in the package with yours and continue to import all of these MIBs, I get another error but with LAG-MIB regarding BITS not being found.
Older Dell-Vendor-MIB.txt was already bundled with NetXMS. I've pushed new version alongside with N3000 MIBs to our git.
Snapshot of mibs directory attached to this message.