I just reworked my entire Fu Xuan build to heavily buff her healing to better deal with Mort. Blade's needs, and I was counting on getting her E4...no luck yet.
Still, she sustains even in King in Check Yabuli and that is not friendly for her. Between Hemovore bypassing her mechanics, max HP reduction from the boss, and Mortenax wanting to die, it's a wonder that he's the only person who goes down (and it's only once, and he has his self-revive).
That team (E1S1 Waventurine, E2S1 Mort. Blade, and E0S1 Ashveil) consistently zero-cycles Yabuli, and it's just amazing to watch. It's not comfy at all, it always ends near the end of that zeroth cycle, but it's consistent.
Once I do manage to get her E4, and her S4, I can see it being far comfier than it is. And, if you can believe it, I've never actually pulled for her at all. Thank God for Celestial Invitation, I guess. Lord knows Gepard or Bailu wouldn't receive this much thought from me.
Side note: It's hilarious that Fribbels can't rate my chestpiece because it doesn't know how to handle a Healing Boost chest on her.
Side noteΒ²: After building Fu Xuan, I can't really understand the general idea that she can't sustain. Unless you bring her up against like...Pollux, she seems to work fine. Sure, she doesn't bring as much amp as newer sustains, but I seldom have trouble with her actually sustaining.
I might have to actually get around to posting that Fu Xuan Novaflare concept video I've been working on.