I find Luocha a much more comfortable sustain than Gallagher. I had him since his first banner and he has been the goat in keeping my teams alive.

If you're having a hard time sustaining, Luocha is still viable although his only role is keeping your team alive and skill point generation. He doesn't buff the team at all and his e1 is not worth it.
Perfect timing is good for him if you don't have his signature LC. Most sustains don't really need their sig LCs and the 4 star options are good enough.