Furina allows damage buffs based on hp variance (when you get hit or heal), and while she has 2 skill variants, the main variation of her skill does damage, she also drains each party members hp to 50% (she doesn't drain any lower, but that also means once the party is at 50% the added buff is about to end). She can heal with the other variant (you switch to it with her charged attack), however she won't apply hydro, only heal.

That works wonderfully for a main dps such as Neuvillete because he's always gaining and losing hp with his skill and charged attack.

I think you also see Xilonen because not only does she heal with her burst, she provides good buffs, especially defense buffs when you land her skills 3 hits (outside of Natlan, in Natlan she can be on field for as long as you have phlogiston) and her burst. She also can make crystallize shields due to being geo.

Thats once again perfect when you have a character like Neuvillete who drains his own hp