I think GP's barrels should have damage scaling with crit chance, but are unable to directly crit
As is, whether or not a barrel crits in a fight very largely determines the outcome, on ADCs crit is more balanced since they attack many times in a fight, but GP only has a few chances to crit in a fight with his barrels, so luck ends up becoming a significant factor.
Thus, I think that GP's barrels should scale with crit chance without actually critting, so that the damage is more consistant. Additionally, if this change actually occurs, IE should give a 50% bonus only to the damage from this crit scaling so that it retains the same value on him as before.