I loot almost everything off of corpses. At least the things that go in keys, so, Potions, Reagents, Meat,Scrolls, augments, gems etc. I make sure to have all of the decent dropped artifacts on my grab (things like Antiquity, Tactical Mask, Fortune Armor, Gloves of the Hard Worker) i also have Pickaxes and some other things because i can stuff them into my tool box.
The lootbag is wonderful, it just takes a bit of time to set up. I need to take a day and reset my lootbag, it's gotten so long that i cant ever tell what i have autolooted and not heh.
A good rule of thumb is to turn off the things on a lootbag that you cannot sell/store in keys. So things like Armor, Jewelry, Weapons, turn those off. Gems are great because you can sell them to a vendor for a decent price. and make sure you have all of the augments on your lootbag, because those arent very common and can be very valuable.
Once your lootbag is set up correctly, it makes killing and looting so much easier. If you use steam, you can even make a macro to automatically stuff items into your keys.