I use a plug-in (feat artists in titles) that negates that unfortunate MusicBrainz decision (I never noticed it), so my tracks scrobble fine to Last.FM. YMMV, of course.
I'm specifically talking about "Display Artist," which I believe MusicBee uses to scrobble. I have guest artists put into the title and also tagged out as ";" artists. If Brainz puts them in Display Artist, I manually separate them so only the main artist is listed as Display Artist.
I'm, of course, not trying to dictate how other people tag their files. I'm just sharing what I've found to work pretty much across the board. Use the info, or don't use it at all, as your specific situation warrants.
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