I think the Guard skill should be removed as the normal sorce of making your shield do it's job. Instead, your shield should automatically block. determined by its Blocking value and if you are wearing the optimal rank shield. In addition, Deflection, Aegis Boon, and Outmaneuver should be switched to set times instead of dependent on the shield wield rate and if you have self-preservation equipped or not, Altered by if your shield is the proper rank. Given that, Self-preservation can be changed to increase shield blocking rate instead of the duration your shield arm is kept up.