I have noticed the same counter rate being curiously lower when I use him in GW and LS battles. That was before the recent patch still, but I will be tracking my battles now that include him, just thought it could be bad luck until this post...???
I usually am not so pecamistic about the odds in this game as most of the forum posts but I was intrigued by this OP. I just got him to 5* and full gear recently so I was really paying attention to his counters but that 70% counter chance (yes, max ability is unlocked) seemed not to happen that frequently.