Awesome to all that, and thanks for your quick response!
The moving QTE would just be a square like what you've got already, could be a solid shape or just a line drawing, but it wouldn't move by itself. Instead, like shown in the Clair Obscur vid, there'd be a smaller shape (maybe a circle or very small rectangle) that traces the edge of the square, and you have to time your button press to land on the target edge, which would have a different color than the rest of the square. Hitting this different-colored edge would guarantee a critical hit, while hitting anywhere else just gives a basic success/normal damage.
Also, I'm thinking, failure to hit the QTE at all (including at any point of a chained QTE attack) would result in either a) failing to launch the attack at all, b) reduced damage output, or c) interrupted combo animations and damage (assuming it's possible to have multiple QTEs trigger in sequence with animations?)
So basically you always have a 25% chance to crit, assuming your reaction time is good.
And, heh, apologies, but here's another idea for ya, for a different way to implement combo chains (landing on the red zones on the ring would give you crits iirc):