Why Overheal's shield last so little?

http://leagueoflegends.wikia.com/wiki/Overheal

Description PASSIVE: Healing in excess of your maximum health is converted into a shield for an amount of up to 10 (+ 10% of maximum health). The shield lasts 6 seconds, and then decays over a 2-second duration. Receiving healing, dealing or taking damage will refresh the shield duration to 6 seconds.

I understand that the refreshing effect makes up for the short duration (kinda of), but even then it still lasts too little. You charge it up on minions or camps, and by the time you're leaving, the shield is gone. Even in tower sieges where the enemy team is hard pushing, there's no time for refreshing or recharging the shield due to how little it lasts.

Now I know that the last change made on this rune was when ADCs were able to abuse it, but it's almost 2019; ADCs are nowhere near in a position to abuse it. I really wish to pick it on fighters who synergize well with it, but it's is pretty weak on pretty much everyone (with some exceptions of course). Is there any possibility to buff its duration a little, like 6 -> 8 seconds?