Shield Bash should have another activation condition
Before I begin, I leave here what the rune does:
Effects While shielded, gain 1 - 10 bonus Armor and Magic Resist based on Level.
Whenever you gain a new shield, your next basic attack against a champion deals 4 - 22 [+1.5% bonus] (+8.5% New Shield Amount) bonus adaptive damage.
You have up to 2s after the shield expires to use this effect.
First, how many champions can't activate this rune with their skills?
#110


And how many can?
#37

At first glance, it's not a bad number, but if we start reviewing case by case....
We have 6 champs that these shields are passive or very difficult to take advantage of the rune.
(I don't know if the passive counts)

We've got 31 left.
Others would be illogical to use this rune in this branch, like
W+AA?
E+AA?
¿Lantern + AA?
R?
I could go on and on with rare examples, like Ekko with his W or Ryze, but that's not the point.
In the end this rune is only viable for 15-20 champions, mostly supports that apply shields, and even for those who can apply it, the Resolve branch is not the best for those champions.
So I suggest, somehow, this rune can be applied by more champions.
https://i.imgur.com/QlXHcYf.png
TL:DR Shield Bash can only be useful in a low percentage of champions (15% approx) and I think that the activation conditions should be changed to make it for more champions.