Jarvan IV good grade?

I can never seem to get about a B or so when I play J4. As far as the after game screen goes. I was wondering if anyone has any suggestions as to what i'm doing wrong. My grade doesnt seem to change between games when i gank a lot and take kills from when I play full tank and give out all of the assists. These are two examples. I want to improve my gameplay with J4, as I would like to get my mastery to 5 with him. Any suggestions would be appreciated, thanks.

taking more kills for myself: http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/2054238240/201762138?tab=overview

full tank and assisting: http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/2081822148/201762138?tab=overview