I just want to point out that you're comparing three different roles one by one here, instead of seeing that Ninian does all these things at once for you whilst only taking up a single character slot.
Since your main team is so heavily physically lopsided, isn't Ninian perfect for you? Blue dancer that hits res, warps, and has a high res stat. Yes, Azura is both blue and high res, and does have better all-around combat, but if you're using the version of your team without Robin, Ninian can do something that you're lacking in.
I'm not exactly trying to change your mind here, but I just want you to know how good an option Ninian is to have for your team, and may allow you to be more successful with a Ryoma/Ike/Frederick party and beyond that, in crafting more versatile B-teams. More options is always a good thing, I feel!
No worries if you really don't want to use her though.
EDIT: on topic, I managed to get what I was looking for out of the mage banner (Sanaki) after four full pulls! She's +Res/-Spd, which I'll settle for. Really happy to finally get her! Now back to saving for Celica.