What Shay-y said :) Shatter is a finisher - you can't use it unless you get the girl's HP and WP down to their lowest point.
Everyone's in the same boat, experience-wise, when it comes to this challenge - the new combat system is completely different to the old one :)
Also, the system as it stands is finished. I will be adding more skills, powers, buffs, upgrades, etc. as time goes on but that will be constant throughout the rest of development and won't affect the core mechanics or systems at all - merely make them easier or provide more variation.