You need to factor Royal Authority into its combo though. All of those abilities are gated by their combos so it only makes sense to average out the potency of each chain. Also Goring Blade is gated by a combo while Scourge is a stand alone 500 potency DoT.

Royal Authority - 230 avg potency.
Rage of Halone - 203 avg potency.

Power Slash - 223 avg potency.
Delirium Blade - 226 potency.
Dark Arts + Souleater - 266 avg potency.

Paladins also can't just spam Royal Authority if they are MT, it builds less threat and has no debuff, so they need to weave Rage of Halone in bringing their DPS down. When I DRK I have to use Power Slash with Dark Arts one time in a fight and I won't have to worry about threat anymore. From that point on my typical rotation is Dark Arts + Souleater into Delirium Blade, rinse repeat, with Blood Price on CD, regardless of how much I get hit that combo is sustainable. Average potency for DA+Souleater/Delirium Blade is 246 potency.

Paladin's weren't given Royal Authority and Goring Blade to push them ahead in DPS, they were given them to just try and keep up.