I pretty much stand on the same opinion. You will usually need 2 mages in most situations (if not 1 or none). Mehlis and Barbie are your go-to choices here. Barbie as the powerhouse, Mehlis as the alternative (her skill can be really useful in some maps). Your silver mages should be used due to their cost, so if you happen to be able to CR either Valerie or Pallis (and you don't need these copies as materials) go for it. I would focus on Pallis to be honest if you can put copies into her because that will guarantee SU for her. That means you will have a low-cost mage with the option of a boost ATK-wise if it really has to come to that. I feel you shouldn't need Valerie's skill in most situations anyway and by the time it's usable you would have been able to deploy Barbie and his skill would be up.

If you don't want to spend extra resources, I'd advise on just going for Barbie and stay with Val/Meh/Bar.

Just my two cents.