I do not think the Combo system is going to be a sufficient replacement for these skills. Damage wise, yes, they will most likely make up for the lost of these skill, but as far as being engaged in combat I highly doubt it. The combo system is in essence just performing two Weapon Skill in succession. Sometime you will have to move position, but that is no different from any ordinary fight. Combos will not require you to pay as close of attention to your fight and with a 10 second window they will not require any quick thinking.