I prefer the rigid system. Part of what makes MMOs fun for me is learning my role and performing it to the best of my ability. Without defined roles, all of the classes play the same and leveling up the other classes for the skills becomes a redundant experience.

Not that an open system can't work, but IMO it was too open. If cross class skills costed more points to equip, or more were locked to their respective classes, it might have helped the situation.