Tianzhu drops! Worth it?

Farming the Flaming Mountain for Merit Talismans and then doing Tianzhu is probably the most AP-effective way of farming for Pork Buns/Immortal Peaches/Divine Pills (just assuming you have no bonus CEs at all, it's almost 4x as efficient as running the 20AP/25AP quest for Buns/Peaches, and 2x as efficient as Ascetic Journey - Expert for Pills. Once you get any Merit Talisman drop CEs, it becomes even more efficient).

However, clearing consistency is also important since SQ is precious. If Tianzhu is too difficult, then you can farm on the easier quests.

For me, Tianzhu is easiest if I can bring a Rider (Santa Alter works), plus a high leveled Lancer and Saber (single target if possible). I build up NP for everyone on the first two waves (I use the Rider's NP on the second wave if both the Saber and Lancer have their NP ready), and then I unleash NPs on Karna/Arjuna on the final wave.

If you need to level up your party some more to make it easier, you could farm the 20AP meat bun quest instead and buy out the shop's EXP cards first before trying to farm Tianzhu.

i personally never spent quartz on revive, more so for event quests. End of the day it gives you CE and ascension materials, both are good to have but not must have (since you can always farm in the next event, and the next...)

I clear Tianzhu consistently with Dantes, Waver, Ushi and Lancer alter, with mystic code combat uniform. Use Ushi NP on asura then swap her with Lalter at boss stage. Dantes is rly just there for the love <3
You can alternatively use Cu for lancer Alexander and George for rider. Support Waver rly help to pop NP on asura and bosses.
There is also a choice to brute force through the quest using Herc/ Cu alter carry.

Personally I don’t think using quartz is worth it in events. If you have to, try clearing the quest with some command seals for extra NP or healing. Quartz is limited while the event shop stuff can always be farmed another time (besides the CE).

If you have a friend that has a level 100 jalter you can beat the quest. My party consists of a Level 35 Leonidas, Level 60 Shuten-Douji and Mash as a sub member. I use the last two spots for Li Shuwen and David with the pork bun CE.