About the slice,
thanks to everybody's reports, I checked more closely the bounce with heavy backspin, and I had based the new formula on the wrong parameter, making the ball slow down too much kinda randomly.
It should be fixed in the next update, although in my tests before & after the fix, I felt it was as easy in both cases to do an acceleration out of the slice, so maybe it'll still need some more tuning, depending on your feedback.
Oserkos,
don't hesitate to voice your concerns, as long as it's done respectfully, it's good for the game, and thus for everybody..!

Someone on Steam had reported the same issue about the high drop shot ; after investigation, it was happening only when standing a bit far from the baseline ; it'll be fixed in the next update.
Overall, the drop shot shouldn't be effective except if you have your feet on the baseline (or better, inside) ; like this, I think it's now significantly harder to catch a drop shot than before, both for the human & the CPU.
For the slice curve, it's alright for high backspin, but not much for medium ; I'll see if I can tune that for the next update, but it's tricky...

Note : you sent me a Bug Report but didn't write in it what I should check/see.