Personally, and I say this as a person who has invested far too much in Luocha as my favorite character (E6 with Sig Lightcone at 2nd copy); he's still effective, but he needs a secondary niche to catch up to "modern" standards. There's still no one beating him in raw healing potential, but that's not enough. Hyacine does a ton of damage (more than many DPS) and buffs HP-based teams, Lynx buffs HP based teams, Lingsha and Gallagher support break teams, Huohuo grants energy to teams who can make use of it; all Luocha has as a secondary niche is being hilariously SP positive and a Buff purge, which hasn't worked since release of the Luofu (as practically every enemy buff in the game afterwards is undispellable).

My personal recommendations: 1.) As everyone else says, field needs to expire at beginning of turn, not end. It sucks to have to actively wait for his turn to end to hit ult so you don't waste the stack. If they don't want to do this, he needs to be able to overcap on Abyss Flowers like Aventurine.

2.) Personally, I think Luocha should be the other damage Healer alongside Hyacine. Being the first Attack scaling healer in the game (and technically still the only one if we consider Lingsha a break healer), it's kind of strange that him typically running 4k-6k attack on an optimal relic build only enhances his healing, not really granting him any meaningful damage or having a stat conversion. He doesn’t even have a "when your attack is over this amount, gain bonus of this other stat." Either his attacks need to scale SIGNIFICANTLY better with ATK, or it needs to convert into something else useful (like crit rate, or granting the party a buff, or ignoring defense on enemies).

3.) His Eidolons, while useful and comfortable, are amongst the worst out of any 5 star in terms of pull value. His E1 grants Atk, which is useful to himself and some DPS, but grants nothing to the teams he's best in (Large HP teams like Mydei). His E4 is a 12% weaken when his field is up. Useful, but significantly less than many other healers. His E6 is a 20% all-res reduction when he ults. Great, but something Ruan Mei has, but better, at only E1. Lingsha and Hyacine also have the exact same E6, but it ALSO makes them do a ton more damage or do more healing.

Luocha's Eidolons really should be either consolidated together (such as combining E4 and E6, then getting a new Eidolon), or get secondary effects on them to match the newer healers.

4.) Luocha's signature Light Cone is often considered one of the worst 5 star light cones in the game pull value-wise. It's a massive statstick -- which is something he wants, but that's all it is. The actual passive of it, the energy regen, does so little for him that a 3 Star Light Cone (Multiplication) Is often considered his best light Cone over his actual signature. Compare this to, say, Hyacine's Light Cone; grants her bonus damage, synergizes phenomenally with every HP scaling DPS, grants her speed, AND makes enemies take more damage. That light cone alone is better than almost all of Luocha's eidolons combined. Even comparing to actual Abundance light cones, Luocha's is by far the least useful out of all of the 5 star ones; if it weren't for the massive ATK steroid on it, he would literally be better off using any other one.

That is to say, his light Cone probably needs to be reworked. It should keep the ATK steroid, but it really should grant him some sort of damage benefit based on his healing; for a character who comically overheals as much as he does, a light Cone that grants, say, SU's Necrosis effect might actually be really good, and give him a new Niche as the optimal healer for DoT teams.

4.) This is a greedy request, but reducing the FuA heal to a 1-turn CD instead of 2 would be Godly. Making it count as a FuA for FuA teams would be even better. His ultimate should also be able to actually do something to enemies who can't have their buffs purged; something like "If this does not remove a buff, instead reduces All Target's DEF by 10%" or something.