(According to google)
•Barbara
I currently use Barbara as my healer for Xiao and so far it's good buuut I've also seen a lot of players use Bennet since he's also one of the best healers in the game.
•Jean
Jean places a regenerative field on the ground similar to Bennett, but she also instantaneously causes HP regen, so if you stay within that field you can get your HP restored to full.
•Qiqi
Qiqi lets Xiao get healed as he does damage, which is what he does best. Jean is a better character than general than Qiqi. But Qiqi's heal, while definitely problematic, are vastly overshadowed by the sheer healing output.
According to google People say that these three are the best healers/suitable healers for xiao.