tribal and bronze buckler stats reversed ?

This is how most shields work - Every level may mean more of one defensive stat, and less of another, so they're not always a flat upgrade, and you have to make a choice. However, the increase in block chance is probably too high. Block is usually a much better defensive stat.

Hmm, I'll investigate further!

Edit: True! Sorry, I assumed you were meaning something else, but they do go down as the tier increases - I'll talk to our balance guy about it.