One thing I never see is a Ret paladin swap on a shield during defensive times. In both PVE and PVP.
I think it would make sense if Ret Paladins swapped to a tank weapon and shield during moments such as Heroic Lord Marrowgar's Bone Storm.
And also maybe when getting focused in 3v3 by two melee classes.
As a warrior I find myself switching to my shield all the time, although ret paladins don't have the shield block or shield wall talent, the shield itself is still a huge armor boost.
Why do Ret paladins never bother to use a shield when it could prove useful?