I don't agree. I've used the short slice quite a bit to force UEs from my opponents. If I had to choose to have the slice overpowered or underpowered I'd say underpowered would be the way to go. So in that regard I'm ok w/ the slice.
I know your guy is slice invasion so you relied on the slice quite a bit, but from other players' perspective the slice was far too dominant and you'd see things like slice rallies and slice passing shots which barely ever happen IRL. And it's still possible to hit good slices, just not as easy and not as strong. All in all I have no problem w/ that part of the update.
And FWIW I have played a few matches w/ Fed since the update and am still able to win with him. You can't rely on the slice as the main aspect of your game, which again I'm ok with since what pro does? The slice is primarily a defensive shot meant to draw errors as a change of pace, not an offensive shot. So in that regard the update has it spot on.
And from what I've seen slice returns are still quite useful when use correctly.