A true LoL classic: Yi tanking the fountain turret
I'm not sure, but I think what's going on here might be that the old fountain turret did physical damage rather than true damage. If so, I'd consider this an extreme demonstration of how healing becomes more valuable with resistances.
The Randuin's reminded me: old Yi got a stupid amount of Armor and MR from Meditate, instead of "damage reduction" as such. Randuin's scaled on Armor/MR, so he could pop it while meditating to slow people for like 10 seconds or something crazy.