I've done some playtesting on my own with the new system. Overall, the die system seems to be working okay. I can stat up two people have have them slug it out without any major difficulties.
With one exception: damage.
Damage as it currently works is like hitting people in full plate with papercuts. Someone will eventually drop, but every single fight will be interminable. That's because your damage is based on the margin of success of the attack roll and nothing else, and the margin of victory on an attack roll tends to be a point or two, almost never higher.
To resolve this, I'm setting the damage of an attack at the margin plus the total effort of the attack. That means that even dice that don't come up successes still factor into the hit (assuming you connect). This has the happy side effect of making people more dice hungry, thus encouraging endangering hopes and spending more destiny.
This does make multiple attacks, such as those granted by some potencies, less effective though. You split your effort pool to make multiple attacks, which now have a lower chance to hit and do less damage to boot. Not a good deal. To make up for that, multiple attacks do cumulative damage in terms of effort. For example, if you make two attacks, one with 3 effort and one with 4, the first attack will do 3 + margin damage. The second, however, will do 7 + margin damage. 4 for its own effort and 3 for the effort of the first attack. If, somehow, the character had a third attack too, it would add the effort of that attack to the 7 total effort of the prior two attacks when figuring base damage.