I would hardly classify Verotte as B-tier. she's pretty much outright useless. fact is, Giovanni outclasses her because range is what you use a pirate for, and Giovanni has it going for him as a male while Verotte is just...nah.

which actually comes to one key thing: are you basing this on DMM stat patch, current nutaku status, or current nutaku units based on their potential in the future?
because Stella is only B-tier based on potential, C-tier based on current. Also if based on potential, yuyu would be B-tier instead of C-tier, because after AW she beats Cloris by a wide margin. her higher attack speed also makes her a better choice when it comes to clearing some risky strategies, in particular the current DMM event's 7 stam map: https://www.youtube.com/watch?v=pFEoMBI5Oe0
following that strat by sennen war, I actually placed yuyu where he placed calliope. granted calliope's attack speed does the job as well, but I find having yuyu's attack speed makes it safer.

Betty is actually B-tier by DMM standards, due to gold farming. and if you can skill AW her she's probably your only reliable assassinator.
I also find it hard to put christopher and Dorca is 2 different tiers. granted dorca would likely be the choice for 3rd healer, but fact is she's not actually much better than christopher, and christopher has it going for him as a male. which is why I also think she's only really B-tier.

as for Pallis, A-tier is right, but I wouldnt say she is S-tier. sure she has higher attack than valerie by a fair bit after affection, and her attack up skill is much better, but as a beginner, I went with leveling valerie because I needed him as a male anyway and he has much better attack ignoring affection boost (and hell if I have enough affection items for Pallis I would've been a veteran)

Elaine and Calliope are seriously lucky to even be placed in A-tier here. by DMM standards both would be nothing more than B-tier.
Conrad isn't D-tier btw. sure he is harder to mincost compared to mortimer, but hell he still has better hp and atk than mortimer, and works way better than him as a duelist. deserving on C-tier IMO.
Robert is B-tier. sure trust items aren't worth much, but hell he still is a male healer that also can eventually be AW'd. just that makes him deserving to be on equal terms with christopher, and arguably even better.