Items or a rune that deal extra damage to shields? Also concerned about Precision keystone runes...

So I want to talk about heals and shields at bot lane in general. As a long-time player, I feel happy that most champions and items are viable as they are in Normal and Ranked games right now. However, after watching World Championship, after I saw so many people blame Bang for SKT's loss, I couldn't stop thinking about those clutch teamfights. As an ADC main, I have also encountered this situation a lot of times where I almost killed an enemy and suddenly they just got so much healing and so many shields that their HP bar became almost full again. Against healers like Soraka I tend to buy Executioner's Calling to make my life easier at bot lane, but what about shields ? I would really love to see a Lord Dominik /Mortal Reminder equivalent that specifically works against enemy shields. As a matter of fact, it would seem unfair to just simply add an item for ADC to peel down shields, so I think it will be better and more interesting as a rune.

As for the new Runes system, I am actually confused about Fleet Footwork (or Warlord's Bloodlust in the old mastery). It has been changed from "scaling total ad that's affected by critical strike", to "fixed amount + bonus ad" that doesn't seem to be affected by critical strike anymore. After doing some simple math, I figure that it now works better at early level (5 health gain per proc at level 1, comparing to the old 2-3), and is significantly worse later on (~60 health gain with full items, comparing to the old 100-120), not to mention that it no longer benefits from crits.

To be honest, the only time where I find myself needing that regen, is when my support is not a healer/enchanter. When my support can heal me or shield me, why would I want that regen? I think the other two keystones are both great options for different ADCs, as one gives burst damage when the other one grants sustained damage. Whenever I take a look at the Precision path, Fleet Footwork instantly becomes an inferior pick for me, because it is limited to one situation. On the other hand, why would I pick a life-stealing rune when my support is an aggressive melee support anyways? Shouldn't I be following my support and kill my enemy as fast as possible? As a comparison, the Sorcery keystones seem way more balanced with a poke, damage/shield, move speed setup. For example, Brand is a really good mage that is able to do tons of damage over-time, but is only able to get there if he can get away from enemy front line. There are many other mages like Xerath , Lux who can benefit from bonus move speed without the need to worry about their damage output. In a world where the only job ADC needs to accomplish is to output damage, I don't think Fleet Footwork is at the same level with Press the Attack and Pethal Tempo.