Might as well drop an absurd example of Hydrangea usage here. https://streamable.com/oa1yq
A small breakdown in my setup:

Since the the team will be encounter three fights will different weakness, may as well use just crit promo on Yarrow, hp on RR, and provoke on Hydrangea.
With Lantana's support, the setup has 100% skill act or close as long as long as Hydrangea gets hit. Lv 1 skill is .24*1.9*2=~91% skill act rate, as long as it's higher than level 1, it's 100%.

1st fight is not much a problem after the def buff wears off, it can be nuked normally with enough atk buffs.
2nd fight is probably the riskiest part of the whole thing, as the party only has up to 3 turns to take out the boss. My only risk here is RR or Yarrow not procing crit, as they only have 50%.
As the leg part does only a little over 20k, any girl ampied or defending will be capable of tanking a hit without def buff or debuffs.

Final fight with Mother is a joke for this party since there's 6 turns, plenty of room for error for crit to proc.

Although my regular farming runs looks a bit different, two parties instead for consistency at the leg fight. Here, I can let RR run loose with weak promo skill. https://streamable.com/f5bxv