3.0 has improved knifefighting builds greatly, but that backflip has been left behind, and made less useful by adding a stamina cost.
Problem: it doesn’t combo into any other move, unlike the standard roll. You can’t interrupt attacks to do it, you can’t chain it into or out of attacks, all you can do is stand flat-footed while your avatar’s other animations finish, and then you can’t influence the direction it’ll leave you in. When it’s done, congratulations, you’re out of attack range, so what do you follow that up with? Moving in or waiting for the opponent to move in? If you did a directed roll instead, you’d know what to follow up with.
I like the animation, but the end result isn’t worth anything.