Reposting toly's post in the forehand thread...
Arrrg. Perhaps hypnosis would help
IMO the main problem is a toss.
At contact the racquet long axis is vertical and can produce sidespin only. There is no way to create topspin. You can hit flat or slice serves without any topspin. Thus reliability of the serves could be very low. The toss like that can afford people like Karlovic.
Sam Stosur shows two extremely different tosses. Racquet long axis is never vertical, but tilted to the left due to she has never tossed the ball on right side of her body.