Hi there! In my opinion, Karin's skills and status is fair and just right .. Actually, she's like shizune, both can heal and poison in the same time but .. If you're talking about the Chakra Chains used to control Kyuubi, then it's impossible for the game to add this to Karin, since if we put priorities to this game's characters with the Anime Characters, Karin is only a Supporting Characters, unlike Uzumaki Kushina who's one of the Main Character Roles in the Anime, in this game, the other Kushina ninja(the one that is angry looking and her hair is floating) has the skill Chakra Chains, dunno what the correct skill name but yeah.. she have that, makes adding this to karin is impossible ..