The upgraded Bronze Buckler can parry trolls well so its useful.... Iron Buckler on the other hand..... the problem is the Draugr archers... they will guard break you with the buckler. so getting the banded is shield is probably preferable (however the devs are probably going to add the ranged parry back in next patch according to testers). Where the Iron Buckler really shines though is early Mountains if you are trying to parry golems.