[Sarinpa1]

In cases where knockdown needs to pass a hitcheck to proc, this new addition that reduces evade would be likely alright, with the proposed change, or with a flat reduce. (Percentage is incredibly unforgiving.)
Turnover is quite the issue as was mentioned, but I'd say dense thunder falls into the same category. Six ki is very, very easy to come by, and we're back to the issue. Dodgy characters that are not study for one reason or another shouldn't be completely destroyed by something easily accessible as knockdown.
Based on a few tests, knock-down madchop will very much kill everything that counts on evading, without having the very specific classes with large evade buffs. (Mainly mages in trouble, yes. )
I'd personaly not touch knockdown skills themselves, rather just tweak the penalty.

(Also when i said buff dh, i was kiddin sheesh)