I don't think line of sight being a requirement to heal is too much of a problem. Actually, it might be a necessary balance feature considering the fact that you can heal allies from quite far away. Io's heal isn't the best, but it's quite flexible as it is.
Io healing sucks because she has EXREME amount of utility, similarly to Jenos;
- 25% Damage reduction
- 40% movement speed for up to 3 allies at a time.
- 1 sec long stun that GOES THROUGH SHIELDS and is arguably the easiest to apply in the entire game.
- Ability to proc overtime from far away
- Amazing contesting posibilities
- Ability to do 5 man zoning
Not to mention you require 3 items to counter her.
Obviously, she pays for these by having weak healing and weak ultimate. Otherwise she would be a walking powerhouse. Don't underestimate her.
That being said, I think she needs more range on her healing, for 2 reasons:
- She has no way to increase it and it's rather short when compared to other supports.
- It is very counterintuitive when you use your dodge and get out of your heal range.
Then she will be fine. She is my highest winrate champion currently and I have over 7 h on her already, sitting at around 70% winrate.
Dunno about it needing more range range. It seemed to be quite very long ranged from what I tested myself tbh.