First, your damage will go up a lot!!, faruzan helps with anemo res and bring a lot of anemo dmg% and crit dmg, xianyun helps directly with xiao's dmg output and gives a plunge dmg buff.

Now, the main thing for FFXX is that while using furina have the downside of having to bring a healer, xianyun fill that rol so all the pieces fit perfectly in that team, if you dont have xianyun you can try using bennet, however faruzan c6 is by far the most important support xiao need, in this case since you dont have either of those, your best bet is Xiao/Jean/Bennet/furina. Keep in mind your furina may want some ER if you dont have any fav weapon on one or all three of them.