THP does not stack, which makes it only good in combat, while actual healing is good in and out of combat.

Does Twilight sanctuary temp HP stack?

Since temp HP doesn't stack, they choose whether to keep the new roll or their old/remaining temp HP. Alternately they can clear a charmed/frightened condition without a saving throw. This continues for a minute, longer than most combats, and does not require concentration.

Is Twilight Sanctuary op?

After a bit of test play, my DM and I are feeling like the Channel Divinity: Twilight Sanctuary ability of the Twilight Cleric is a bit OP for tier 1 play... 1d8 of temp HP per round for the whole party plus clearing Charm or Fear, every round, with no concentration, is a bit much.