If you have to DESIGN encounters to trivialize it, then it's OP.
And if you have to DESIGN encounters to make it OP then it is not OP.
But more to the point, name another level 2 cleric ability this good? It's not just about OP or not ir's about even a semblence of balance.
The Twilight Cleric's own Eyes of the night (a 1st level ability

) is better.
If we are talking strictly
2nd level cleric abilities
1. Harness divine power is worse levels 2-5, about equal at levels 6-12 and better at levels 13+
2. Arcane Abjuration is better (although the rest of the subclass is awful)
3. Artisan's blessing is better
4. Knowlege of the ages is about equal
5. Order's Demand is about equal
6. Balm of Peace is better (because it brings up downed allies)
7. Destructive Wrath is better if you multiclass to leverage it (worse otherwise)
8. With certain builds guided strike is better (although not generally as good)
I played a twilight cleric from levels 1-4, the abilities are HEFTY. The twilight aura did make fights MUCH easier.
I am playing a twilight cleric, currently level 8. Twilight cleric is the most powerful cleric I have played, but it can't touch the more powerful subclasses like Bladesinger or several of Tasha's Rangers.
In the game I am playing with a TC, the only time we had a party member die (actually die) was at level 5 when the party wizard got hit with a poisioned crossbow bolt while I had TS active. The battle ended the very next turn, if I had went more Nova to start out, he probably would have lived. At 8th level, more often than not I am burning CD to get back spell slots and not using it for TS.
At levels 1-4 is where Twilight Sanctuary really shines, but once you get to level 5 there is a pretty substantial opportunity cost to using your action on that instead of a spell. If someone is charmed or you are fighting an enemy that charms people then it is awesome to have. It is also good if you forsee some big long slug fest where you are going to be adding temp hit points for 8 straight rounds (although that is rare and even more rare that you can predict it ahead of time). If you have a long day where you use all your spells, .... then too it is nice to have this instead of just swinging your greatsword. But in most combats you are going to be better served by opening with a 3+ level spell if you have it because by your second turn, combat is usually half over if everyone is doing their job.
The only thing I have really found that is "OP" is the 300 foot darkvision which lets you outsee just about every other thing in the game. In any dark area with clear sightlines you (and the people you gift it to) will see enemies long before they can see you. You can ambush them from like 300 feet away and they have to dash for 3+ turns before they can even see you. Ironically this ability clashes quite a bit with twilight sanctuary because if you use TS you light yourself up.
None of the rest is OP but in combination it is unbalanced compared to other clerics. You get an initiative bonus AND martial weapons AND heavy armor AND TS....