Why is Luvia so low? Shes at least EX-

I think she's kind of overrated. I don't like the crit stuff in her kit because she's an arts servant who will almost always be going against neutral. I don't like the defense buff because you're probably going to use it on herself and being an arts ruler, defense is much less value than another type of buff would be. The attack buff isn't too strong, and the arts buff is only one turn. The only reason I put her as high as I did is because she has a common super effective multiplier on a pretty spammable arts NP.

Back then I thought Jeanne D'Arc was the strongest servant. Now she is just a great servant.

Astraea is definitely too low. Even to this day she's cracked. Arts servants are the ones that better utilize crits precisely because it enables them to loop their NPs like crazy. Also, she has Ignore Invul on her NP, which is the best place for one to have this effect. This is one serious advantage she has over Kagetora. EX tier for me.

One unit I do think is terribly overated is Alter Nitocris. Like, her refund is bad, her damage is way below Spishtar, S. Kama and Mélusine, her supportive capabilities are kinda gimmicky and negligible... even the 100% battery is not amazing on an Arts looper. She's like Summer Kiara but done wrong. B+ tier for me.

The other positions I more or less agree with.

I agree with that point about crits for servants with bad NP gain, but I think Astraea's is high enough that it doesn't make enough difference to take up a large part of her skills, because NP gain is all it's good for. The damage will be insignificant. The ignore invul is nice but not an advantage over Kagetora unless the boss had unremovable invul. For Nito Alter, I like the Super Effective multiplier, and the battery allows flexibility. That's why I had her at A+.