I sum up the Tank Runes in a Passive Aggression Fashion
The only comments on this post that're allowed are passive aggressive remarks.
Aftershock / Grasp (Don't take either of these. They're awful, you're awful for even thinking about it.) Funflinching (Don't take this. Ever.) Demolish, the very first independent rune that is actually useful. Mirror / Iron skin. Yeah, funny. Cool joke. Awful. The worst two runes on the board probably. Oh wait no, kek, wait - I know an even worse one that you'll see later on. Overgrowth: Gain 0.2 Maximum HP for every monster or minion that dies near you. I repeat, 8 minions, 0.2 HP. Oh yeah, by the way - before this you could buy a rune for 2.1K IP that did 0.5% HP - I forgot to mention that. Revitalize, heal and shield an additional . . . 5 . . . % . . . - . . . okay well, you know, if you're low and about to die - because most tank champions that're about to die haven't used their ability to shield or anything like that by the way - will be able to use this benefit to their advantage. Yes, we play tested this concept - I don't know what you're smoking but it obviously isn't what I'm on. Wait though! There's an actual . . . good rune! Second Wind: After taking damage from a champion, heal it offer later. This one is like, actually good and useful.
Guardian (Oh hey look this one actually scales off of like, you know, actual fucking stats that you build - holy wow this one, that's meant for sucking a dude off is like, you know, useful because of it's scaling. Wow who would've thought.) Font-Of-Life, make your other allies: Heal (Your ADC's, because it scales so well with ADC's and no other class on the map.)
Ya'know what though? We aren't done FUCKIN you and that cute little boars ass, Sejuani - we're coming for you. Because of your character class - you won't be needing any damage anytime soon. Ya don't need Precision, that's for actual good champions! And ya don't need domination either - go fuck yourself. You get the options of choosing probably the most worst piece of actual garbage that is the inspiration tree - or you can choose the sub-optimal sorcery runes. Take your pick. Doesn't that ultimate hat sound fun? You get like . . . an extra 20 seconds off of your ultimate that you've already used, on the enemy team that is either dead or trampling over your dead body - because you can't seem to stay alive longer than 3 seconds after your passive pops. Celestial body sounds like a good rune, doesn't it? 100 HP - that's like 1/8 an auto attack from the enemy Lucian, and you deal less damage so that means you are more tanky! Wow minion dematerializer - so cool and useful! Sound good to you, Sejuani? Does that interest you, Sejuani? Fun to you, Sejuani?
Well you'd better get used to it, because in League we don't need balance when we've got

Oh btw we play-tested this for a few months https://youtu.be/CZ1m39K4Tgw?t=11s