Shield Bash is interesting
Shield Bash (R2) Takes place of Bone Plating [New Effect] "Whenever you gain a shield, while still shielded your next basic attack against a champion deals 5 - 39 (+1.5% Bonus Health) (+8.5% Shield Amount) bonus adaptive damage (minimum 4s proc window)."
So I play Urgot top and with his W Shield this looks good.
But in practice its just "Ok"
Then I was thinking of other Champs that have shields

Not sure if I missed any.
The Rune is bugged a most of these.
it does not work at all
at lvl 18 full build can get ~420 damage on the auto attack
I see this being really abused by champs that can gain a shield VERY often because there does not seem to be a CD the bonus damage.
So
All can use it every few seconds.
At lvl 18 its base is ~+85 (+85/1000 hp of shield)
is gonna be busted mark my words. Brb Bork build gonna become meta and he’ll be doing 30% hp per auto
and
will proc this.