P1 is definitely for Kama. She's just simply lovely. P2 and P3 will be Arjuna Alter and Melusine. Didn't use them, but since you ask, this is my answer.

My first choice is Arjuna Alter, second is Kama and third is Melusine

1st place: Okita, 2nd place: Melusine, 3rd place: Kama.

Arjuna Alter, Kama, Okita

On my account, Melusine is the big one at NP4, followed by Summer Okita Alter and Kama, both at NP2. But if I had Summer Ibuki at a similar NP level, she would dominate.

With four being farmers and two being boss killers, they have different jobs anyway.

The only servant I have of these 6 across both servers is Melt so she is defacto best for me. If you want me to rank which ones are objectively the most powerful at what they do I think Kama is now number 1 whether it's recency bias or not her NP upgrade makes her among the best single target servants in the game whether she has class advantage or not she dishes out a lot of damage and her kit is still so good. Permanent guts that doesn't expire until it gets procced or removed by a skill or breakbar effect is amazing and a rarity since most guts are 1 time, 3-5 turns.

After that I think it's Melusine or Ibuki summer for 2nd best. Both are heavily pushed. Then Godjuna or Melt since Melt got an NP upgrade she is top tier single target as well. Okita alter saber is definitely the weakest of these servants.

Melusine And junao

Melusine and Kama, then Ibuki and Melt

Was the Saber-classed Majin Saber's really that good...?

I kept coming across people whom said that it's lacking. (・・;)ゞ

She is a great Quick looper. The biggest flaw is she is a Quick looper. That is rarely something you would want for the current content. I've used her and other Quick servants for my downtime farming loops, but 90+ and 90++ is what people want to target.