I've been trying to come up with ideas for making the shield a bit less broken in 1v1 mode, but I haven't come up with much, other than maybe bumping the price up even higher. FWIW the nicer girls (Denise, Crystal) will never finish you off with a shield. The ruthless ones, on the other hand, will do it every time, so if you're going up head to head with Rosie or Sandra and you're down to your boxers, buy the shield before they do.