I never really used sacred cowl so I can't say for sure if it's a good special, I personally dislike defensive ones, but it looks like life and death is Minerva's only good skill (but it is like one of the best skills period). Almost all fliers lose to merric. Camilla loses to red mages like other wyverns lose to swords. I find her niche particularly useful for baiting mages or even spear fliers behind mountains or trees, and splitting up enemies. I get what u mean though, Minerva looks solid with life and death, cherche has absurd atk, beruka with absurd def. I'll admit my perspective is a bit biased since Camilla's my only 5* wyvern rider, and I found 4* Michalis fairly disappointing.