So, if you stack the % health quints and seals (9%), and you have 3000 hp, you'll get 270 HP from runes.
Meanwhile, flat HP quints and scaling seals will get you ~250 HP
You're gonna have to be Cho'Gath to get health from the scaling runes.
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"What if you just eat vegetarians?"-neonreaper
"^ You are what you eat. ^_~"-Koiji