Take a closer look at Karin's stats; that high HP and low RCV means that Karin will be hit incredibly hard by any and all poison attacks.
Would be, rather. Dual Awoken Karins gives 80% resist, which can easily be topped off one way or another. Attacker typing and all means Neptune is a viable enhance with his row enhance in tow; Dragon typing means both Pirate Zaerog and Draggie function and are on-color.
If you roll with Neptune, you can do an incredibly silly combo with Zeus Mercury and Ruel; 24 water orbs, 3 wood orbs, 3 dark orbs. Maximum water carnage.
None of the mostly desirable heartbreakers have an on-color sub attribute; Physical Vampire might just work out (haha, work out) what with that extra skill and all.
Other options, should you not focus entirely on rows (because rows on a China girl are hard!) include Sachi bros, Uvo Starling, Skuld+Physical Vampire...