If the topspinner is ripped a fair bit, then the dip that you get really does cause all manner of problems to sloggers. Essentially, any batter with slack techniques will struggle when the ball isn't on the length they expect it to be on. They premeditate, plant their feet and get ready to swing. So any ball that dips on them will result in a miss-hit a lot of the time. It's those batters with quick feet who cope with topspinners well, but very few batters (even at high club level) use their feet well.