Make Whirlwind usable in defensive stance. This will increase prot warrior's PVE dps, and help our AOE threat.
Having a 1-h weapon and shield wont do anywhere near the damage of 2x 2-H wpns, but with our existing threat modifiers, it should work about as well as thunderclap. (Also have something put in there so that for the short time you are faced away, you cant get hit by a boss from behind and get wtfcleaved).
Also, (not AOE related, but would be fun) having something like bloodthirst that requires a shield would be awesome...maybe remove the 100% chance to silence due to shield bash (PVP nerf), and put in it's place either a prot-only bloodthirst ability, or something that procs on shield slam crits that restore 1% of max health for each of the next 2/4 melee attacks.
Just some ideas i have been tossing around...