This item has bugged me for a while. It has a strictly inferior status to Steel-Rimmed Buckler, and it's a treasure hunt reward to boot. My suggestion: change Surging Shield Block to Acrobatic Flip or some other improvement. Make Oakenheart Shield into a really neat item!
I would use the Mighty Fist Shield over Parrying Buckler because a: It's awesome and b: I have so many shields I have to scroll down to Parrying Buckler and that takes too long.
I like this suggestion, but it—much like non-critical card changes—is unlikely to happen unless/until we do another round of balance changes.
But, it's worse than Disorienting Block, which is accessible to players, and you can pack a lot on one character. Also has the nice side effect of not changing level or rarity of the shield. (Now, as for whether a Treasure Hunt reward epic should be worse than a slightly higher level rare, that's another question) I ran an elf warrior with . . . 5x Disorienting Block on the Batford map rotation, that was a lot of fun. I'd post it, but I don't want to post my build every single map rotation, unless I start doing something interesting/unusual/high Elo.