I beat the Medb fight last night and it was kinda easy. I went with Mordred, Artoria Alter Saber, and a support Berserk Raikou and Shuten Douji as backup. Ended up being extremely easy since I just focused on Coatl and used my sabers as basically damage sponges. Don't kill the lancer grunts unless their NP is built up or Coatl is defeated. This way by the time Medb gets into the scene, she can't use her move that makes her untargetable. Ended up winning without using a continue. Of the hard fights I've had so far, this one was by far the easiest.
I have two more of the hard fights to do and I'm thinking I might skip them because the dog one is just ridiculous and I'm not sure I want to waste a SQ on it. Sadly, I don't have regular Medb, so I can't use her costume.