Which one would you rather have, extra damage that can be stacked easier (but slower) but only procs when the enemy is at a certain threshold of health. Or lots of extra damage that snowballs hard with lots of damage and procs immediately on your first attack.
Sure the current version stacks way slower and does deal less damage, but it prevents lots of frustrating moments like your entire team (who has atleast one person going full tank with lots of MR) getting one shot from a fed karthus’s ult.
Riot could slightly buff the damage of this current version of the rune, but I think a revert would be extremely bad and very very unhealthy. I do see your side of the argument tho, having access to that amount of damage and being able to stack it pretty fast (especially if you were a jungler) makes the rune very fun, but with the correct champ this rune becomes overpowered, unhealthy and not fun at all for the enemy team.
Thanks for coming to my Ted Talk.