Kindred's on-hit has a minimum damage, and isn't capped vs monsters.
Seems to do a minimum on-hit damage of around 8 times your number of stacks (was getting 66 at 8 stacks), and the on-hit damage isn't capped vs monsters.
Also, needs some clarity on the description that you need to wait about 10 seconds after choosing your quarry for you to get stacks for killing them.