This is weird. I tried BTA with a new download of the 4.6.6 "mv_assets_v.vp" file and that worked okay like you said (Osiris bombers were able to be destroyed normally), but when I tried the new file with other campaigns the Osiris still had the problems I talked about earlier (you would see shield flashes but after destroying the shield hull shots wouldn't register).
Could it have something to do with labeling? In the campaign that things worked right in (Templar BTA version) the Osiris bombers were labeled "GVB Osiris". In the FSport campaign I had the Osiris problem in (Aftermath CE) they were labeled "PVB Osiris". In the post-Capella campaign I had the problem in (Aftermath Reboot II...aka The Blue Guardian), the Osiris bombers had the label "VNB Osiris". I have no idea why that would cause a problem but it's something I noticed.
If I want to play a campaign where I'm facing Osiris bombers I may have no choice but to stick with the 4.6.5 version of this file (like I said it doesn't seem to be a problem with all the new MVPs 4.6.6 files...just this particular one for some reason).
Also FYI: I'm not having problems with other Vasudan crafts as of yet, just the Osiris. On other bombers and fighters, shots register against the hull and they're able to be destroyed normally.