I'm new to game didn't played TE2013 but i played like 20 hours TE4 and i understand the game its really great.
I played few times online and Slices on clay like an Offensive shot it is really difficult to control slices and i think either slices should get minus. or retriever should hit much faster after slice( hitting bit faster after slices maybe but its really not enough) i try to hit great shot after slices but slice is more efficient than my normal shots and very difficult to do acceleration against slices on clay.
It's not defensive shot it is offensive shot on clay very hard to defend against slices.
And one last thing i think in TE4 really difficult to defend. Attacking looks more easy an giving advantage to attackers.