I like Paladin Cecil's character much better, but I don't think his abilities are useful. It basically just comes down to him attacking every round.

His White is useful mid-game...while everyone still has lower HP counts. You can use him to conserve Rosa's MP.

His Cover is a double-edged sword to me. Sometimes it is a lifesaver, such as when he covers Rosa who is about to die. Sometimes it is a curse, such as when you want to let someone die off but Cecil keeps covering him/her so you have to kill them off yourself.

Dark Knight Cecil's Dark attack was useful for getting through those battles with mutliple enemies who were pathetically weak and annoying.