I stopped using the buckler because I find parrying too OP (haven't tried after H&H though) so I solely use tower shields now, and I must say it does a pretty good job.
I currently have the iron tower shield, max upgrades, nothing up until swamp does more than 1 damage. I once accidently aggroed a deathquito, I had 90 health and it took 30 off me (as you might have understood, blocking's efficiency is proportional to max health).
So maybe it's that