10% feels about right… but in reality for less disciplined barbs (ie: almost all of us) it will be higher because we will all do excess stomps for various reasons - before phys cycle, occulus positioning, defensive, etc.
With respect to your last paragraph, the would be true if in theory you were fighting a single target, but who does that outside of the RG fight? Gotta assume constant motion - I can cover a huge chunk of density in 0.5 seconds and lay down a ton of dots in the time that I’m stuck stomping!
I would love to see an experienced high ranking WW Barb like Chris play season FnR and see what they think of it. My hunch is that most will view it as a small upgrade - that 5 second FnR stomp really changes the flow of things and messes with your timings.