There seems to be a lot of variance with controllers, as I have noticed an effect with my 360 pad but a lot of people on PS3 aren't noticing a difference. I'm guessing controller wear and tear may be a factor too.
I'm also using a 360 pad. Tried using varying degrees of trigger press but there was no discernible difference. It's either a block or a normal shot with follow-through. I'm inclined to believe this isn't implemented in the game, otherwise the developers would specify it's inclusion. Nice idea though.
An easier fix would be for normal shots to simply travel less, only reaching the boundary when it's a perfect connection.
Ideally:
-R2 for block.
-RS for standard push for singles and 2s. 3s if well placed, boundary if perfectly timed but rare.
-R2+L2 for an aggressive ground shot. More chance of mistiming, but greater chance of hitting a boundary.
-L2 for lofted.
At the moment the strike-rate is far too high simply because a shot that can reach the boundary is just as safe as a block.