A (different) idea for Barrier
Seeing as Barrier is now a weaker version of Heal, I think that its function entirely should be changed. Here's what I think it should be:
Places a spell shield on you for 1.5 seconds, absorbing the next enemy ability that hits you.
Note that I mean a spell shield ala Sivir or Nocturne, not Morgana.
This would be a big choice to make, and allows the ability on more than just ADCs. Sure, you could take it as Katarina and pop it when you're going to ult, but that means giving up Flash or Ignite. It's not free.