Edit - I forgot to actually say what I came in this thread to say! When using shotguns against high armored targets, besides having Shotgun Surgeon (which is quite powerful in general), you just need to use 12/20 gauge slugs. Not only to slugs decrease the spread of your weapon by 65%, it compresses the damage into one projectile. This makes shotguns incredibly dangerous against pretty much anything in the game. The only real downside is that even with slugs, most shotguns have fairly significant spread, so you don't really want to engage at anything beyond medium distance. Not really a problem with high Sneak or simply being a straight-up boss and getting in your enemies' faces. Some enemies will even conveniently close distance with you only to get a face full of OMG OUCH IS BAD.