Kurenai better healer then Karin? No, she's not. I could go on listing her negatives starting from not being able to dispel debuff (debuff reflect becomes useless once you face a smart opponent), but I wont.

Tobi: Seems good, but in reality it's bad.

Group Shop: Karin

Arena Shop: Nothing. Save your points for when the list changes. Nothing worth spending on.

Ranked Battle: The obvious choice would be Kakuzu. I'm still going for Hinata, because she's inredibly good.

Survival: Kabuto obviously. Has the same chase condition as Karin. Gives you option to freely change in your groups Kabuto/Karin depending if you need the extra dmg from Karin, or the extra body from Kabuto without breaking your chain combo.