Let me put a halt on this real quick. Health stacking is op because they changed the cost ratio of health and resistances respectively. Meaning, it's better to build more health first before any resistances because the cost per effective health. When trying to make something OP defensively you do so buy maximizing effective health. When you have large team comps building large amounts of straight hp it actually diminishes the effect of hp shields.
Basically, for every bump to raw hp a character has the less any additional hp shield adds as a percentage of effective health. However, for each addition of raw hp a character builds the more any additional resistances adds as a percentage of effective health. The new shield comps shouldn't be focused on people getting hp shields but free resistances - Poppy, Garen, Lee sin, Leona, Sona, Taric, Orianna, Malphite, Urgot (his R actually), Elise, Fiora, Soraka (W)
This isn't to say shield comps aren't viable, but if you are looking for optimization, you should be looking for more resistances.
TL;DR - With more hp stacking, resistance steroids are better than hp shields.