In the equipment menu, equipping a shield doesn't change your stats.
See: http://wiki.spiralknights.com/images/3/30/Shieldshowdotheywork.jpg

This could be due to 3 reasons:
1 - Display bug
2 - Shields don't do anything
3 - The listed stats on the shield only apply when shielding and nobody ever tells you this ¿¿??