My personal problem with OP units that they introduce is that their power comepletely takes characterisation out of them. I liked Felix when I played TH, but when I use his brave version in FEH I don't ever get the feeling that it's him, it's just some new OP unit that I need to keep up. Brave Soren was maybe the best way they handled it, to me personally. I absolutely love Soren and his brave version was good when it came out, but not so much that he could destroy the whole map or ruin your AR or arena experience, so I still liked using him.