Just to be sure you know: only certain pieces can even have Bonus Armor on them. Cloaks, necks, rings, and trinkets are the only item slots where you'll find Bonus Armor. For the most part, you're better off going for a Strength trinket, and letting your friendly tank take any BA ones you find; so really you'll just want BA on neck, cloak, and rings (one of which will be your Legendary). That means, in terms of drops, you only need to worry about 3 items with BA on them.