If we merely need a unique AoE component, why not redo Sword Oath so that it's more than an inflexible single-target dps increase, meant only to further slow stance-dancing?

Increase GLD/PLD potencies to compensate for the lost single-target DPS, and make Sword Oath a situational cleave ability, which splits half the damage to be dealt to the target into a split AoE that deals % bonus damage per enemy hit.

Royal Authority combo w/o SwO - 700 potency (+/- adjustment)
Royal Authority combo w/ SwO - 350 main target + 350/n*(1+(.5n)) --> Given n=3, 350 + 875 total potency over 3 enemies --> 408.3 potency per target over 3 GCDs or 136 potency per target per GCD. Compare against Darkside - Abyssal drain (138 ppt/GCD or Maim - Overpower (132 ppt/GCD), noting that PLD AoE relative dps will decrease as n increases.

(A better formula would be to have the damage bonus apply cumulatively, starting from a slightly lower percentile, to better stay near DRK and WAR dmg across a wider range of n.)