Stalwart Defender Overbalance enhancement question

[Bluenoser]

Hello--I've never played a SD fighter using S&B, and I'm wondering if someone can clarify how the "Overbalance" enhancement works. The tooltip says, "Your shields gain On Vorpal: Knock an opponent to the ground." Is this on a shield bash only, or from main hand attacks while a shield is equipped? (Or is it if you GET vorpalled?)

Thanks in advance!

[Rawrargh]

Hello--I've never played a SD fighter using S&B, and I'm wondering if someone can clarify how the "Overbalance" enhancement works. The tooltip says, "Your shields gain On Vorpal: Knock an opponent to the ground." Is this on a shield bash only, or from main hand attacks while a shield is equipped? (Or is it if you GET vorpalled?)

Thanks in advance!

It's on shield bash, as in your shield bashes has a 5% chance to knock an enemy prone with no save.
With the Improved shield bash feat you get a 20% chance when auto attacking to make a free shield bash, this doesn't interfere with your regular attacks and can be achieved while moving (as opposed to two weapon fighting offhand procs). The free shield bash however is capped to one attack per second. Certain shields http://ddowiki.com/page/Item:Bastion_%28Level_25%29 for example comes with an inherent chance for these free shield bashes as well, which stacks with the improved shield bash feat and the shield bash enhancements from the vanguard tree. I did my last life as a pdk pure fighter (main vanguard, sub stalwart) and ended up with around 50% chance to shield bash which pretty much translates into once per second. Combining overbalance with the vanguard capstone you can pretty much CC a single monster permanently and using trip/improved trip/stunning blow/stunning shield when you're fighting groups.