I found a bug in the newest snapshot, 15w31c, in which when you dual wield swords and then block, one of the swords shows you blocking (usually the one in your main hand), and the other just stays in its default position. However, when you view you blocking with dual swords in third person, it actually shows you blocking with both. Thought this was a strange visual bug, so thought I would pop on here and let you know in case you wanna make it look better Ty.
(PS. I have attached some screenshots if you don't understand what I mean)