Katarina is a support
Katarina has no mana issues and low cooldowns, which means she can poke continuously with daggers from safety. She also gets her ability cooldown reset after a kill or assist, which is kind of useless passive in a solo lane, but much more meaningful in a duo lane. Since she doesn't need mana regeneration and cooldown reduction, she can spare money to buy aura/survivability/damage instead.
What do you say?