I love kayle, but Riot needs to sit down and figure out what they want to do with her. Time and again we'e seen true hybrids don't function well. Her pattern is incredibly direct and rather binary, and right now her numbers are just lackluster. Ult aside, there's nothing at all she does that someone else can't do much better. I like ult and E, though E could use a buff back to its old damage with the attack speed nerf, or vice versa. W costs too much as a heal, and doesn't really help much from mobility, while Q is....really flat. Appreciable damage, doesn't slow all that much. Passive I'm 50/50 on: it kinda fits her kit with attack speed, but is honestly more of a tank pattern with the ramping effects.
New thoughts:
Q: Chains of Justice: skill shot that does minor damage, entangles the enemy. Slows and disables dashes, but no other skills. ranks increase mana cost, slow strength.
W: Wings of Salvation: Dash forward to target unit and gain resistances for a short duration. If the unit is a friendly champion, gain no resistances but instead dash back to your starting location, taking them with you to safety. Ranks increase resistances, mana cost, range.