I have been having fun playing kayle with my buddy when we play normal games, but i never see anyone playing her ever. she has good sustain and good harass, and it seems like she could be a solid ap mid, or hybrid top. does she not scale well? or whats the deal. thanks

Kayle is a she....

Heal is too weak to support, Q and E are her only damaging abilities on AP, her range is too short and unreliable to go AD carry, and most importantly, no hard CC, and her movement modifiers are laughable.

Reasons? People read Elementz tier list and only play his top champs. Kayle is not easy to use effectively but can be quite rewarding in the right hands. Armor and MR shred is devastating imo.