Morgana is fine but weak. Here's how to carefully buff her...
#Her ult feels like the likely culprit as it feels like a half of an ability without Zhonya's.
Here's the buff: Increase her teather range after she activates her ult on later levels (2 and 3), without changing the activation range. This allows Morgana to extend her ult influence to multiple people and really threaten the stun if they don't focus on leaving her range or killing her, rather then simply escaping it with a single dash or walking out of it because she has to press Zhonya's.
#R: Soul Shackles
Effect radius: 625 Tether range: 1050
Don't change her effect radius of 625 (the activation radius). Increase her tether range by 100 units per rank up (from level 2-3), leaving her tether range then to 1150 and 1250 respectively on levels 2 and 3.
The one thing that always felt weird when i played Morgana was her ult. It requires out of a squishy mage to sacrifice her range and go into the no-no zone. The risk is too great for little payoff so she almost never uses it unless it's absolutely necessary.
This might actually put her out there as a viable mid laner as then she could be used to threaten a team stun into more initiation with her Dark Binding, as certainly her damage in the kit was never lacking any potency.
