[Priest] Halo vs. Holy Word: Sanctuary

This is comparing the two spells with no buffs (other than Chakra: Sanctuary) and all the same gear at level 90.

Halo:
Mana: 40,500, instant cast
Damage: up to 57,648 to (presumably) 6 enemy targets or same overall dmg to 6+
Healing: up to 96,081 to 6 friendly targets or same overall healing to 6+. This is potentially 576,486 healing.
Cooldown: 40 seconds

Holy Word: Sanctuary:
Mana: 18,900, 0.46 sec cast
Healing: 1608 every 1.84 sec for 18.41 sec (10 ticks) to 6 friendly or same overall to 6+. This is 96,480 healing.
Cooldown: 40 seconds.

Randomly casting Halo in Training Dummy area with no regard to positioning while in combat: 417826 actual overhealing (with Echo of Light added in).
Casting Sanctuary in Training Dummy area on 6 players while in combat: 147908 actual overhealing (with Echo of Light).

Halo HPM: 10.31, HPS ~ 400,000, benefits from Inner Will?: Yes
Sanctuary HPM: 7.82, HPS ~ 8,000, benefits from Inner Will?: Surprisingly, Yes

Soo, which one of these spells is borken? Because one of them sure looks on the side of bad to me...