There's nothing wrong with the wiper mechanism on my 2005 TD5. There's no play, no erratic operation, and they don't overshoot the screen.
So it CAN be right.
On my 1997 300 tdi there's a bit of play in the mechanism, but the wipers are not erratic in operation and they don't overshoot the screen.
On our 2006 90 TD5 the motor was replaced under warranty as the wipers developed play. The replacement parts lasted six years and were still fine when we sold it.
I think it may be due to insufficient grease on the mechanism during assembly, causing more rapid wear?