As I said at the start of this post, in terms of practical use Royal Authority has more of a place after Riot Blade then Goring Blade as it makes sense for a Paladin Damage Combo, the other being the Enmity Combo and use Goring Blade as a stand alone DoT skill like the other 2 tanks DoT skills.

If you get into a situation where you need mana back and if its off a single target (or even multiple targets) your not gonna finish the Riot combo by reapplying Goring Blade dot over and over, you'd be more inclined to follow it up with a heavy hitting dps finishing move like Royal Authority.