As much as this info is extremely useful for those who doesn't have a strong grid and/or 100% eids, there is a tiny, yet crucial problem. And it's about dmg cut eid from friend (well at least what you get from scrolling before going to challenge), it's still pretty rare to run across to find them. People would still equip their event / gacha (like MLB fafnir, etc) eids as main instead, even in phantom main (anzu/vlad/dia domination).

Well if this happens and your friend list equip their best eids then dying over and over at the same level starting from 15+, then it's better to use Joan with at least one healer per level here, only if you DO have like 5 healers/element, but the prob is gacha pool sucks and you have to wait for the CD to allow them to get back to battle.

With this situation, Joan along with her HP weapon is slightly better to use. (unless if have gigaton hp on your team thanks to gun build) 60% + 25% dmg cut is likely better opt to run along with 100% eids.