>My understanding is that these legacies give an extra chance
>to suceed if the initial check failed. Ie anytime you miss a
>dodge with the legacy you get a flat 5% chance of dodging
>anyway.

This isn't too far off.

So for example a dexy character succeeds at the extra check for Dance more often, but the undexy character probably gets a lot more checks because they're already not dodging as much.