-----------READ DISCRIPTION!!!-----------
normal / charge / vaporize normal /vaporize charge
EM sands
7.672 / 22.549(?) / 16.833 / 48.812
ATK%
10.877 / 14.956 / 15.439 / 44.771
HP%
5.301 / 14.797 / 8.314/ 42.909
Small test done with 4piece Crimson Witch.
Though it makes sense HP does one of the least damage as it only gives ATK based on HP%. While ATK% just gives out flat ATK. EM however is a very strong option as Hu Tao is often paired with XQ their dmg goes up really high. The damage up here are taken from the example above.
ATK% seems to be generally great as its overal dmg is huge. EM doesn't fall far off since Hu Tao gets tons of attack from her E and having EM on top of that makes her dmg go insane.
Would Recommend: EM as paired with XQ will do the most damage.
Damage Formula: ATK x EM reaction bonus (Vaporize) x Elemental Bonus. meaning having a lot of different damage types will give you more dmg output.
Weapons recommendation:
1. Staff of Homa
2. Dragons Bane
3. Any 5* Polearm
4. Deathmatch
Artifact sets:
Crimson Witch or Shimenawa 4p
HP/ATK/EM/PYRO DMG/CRIT RATE or DMG
HP/ATK/ATK%/PYRO DMG/CRIT RATE or DMG
HP synergizes very well with her getting ATK from it but it's much lower than running ATK% sands, her HP really doesn't matter as she just wants to be BELOW 50% HP. Using Shields like Diona/Xinyan/Noel/Zhongli really makes her shine.