Just to clarify so people don't assume I mean something I don't due to English being my second language, I mean Put tanks back into the meta, not balance the Meta for tanks, or make tanks the only viable option.
So, the tank meta. Some people hated it, others loved it. The times when Sion, Garen, Cho', Mundo, and many others were the leading damage dealers, and unkillable monsters. However, these times were riddled with toxicity and unhealthy lanes. But, the fall of the tank meta lead to the rise of new metas, The "ADC's do 900 damage crits with 2.5 attack speed and 20% lifesteal so play a ADC's or just afk." Meta, The "Burst Mages 100 to 0 everyone in 0.52124224 milliseconds." Meta, The "Assassin's kill everything in 1-3 hits" Meta. And a few others that found their way in and out of style as well. All of this, thanks to the fall of the tank meta. But, the tank meta needs to come back, but in a way much more healthy and clear.
Here is how it can be done, theoretically.
Gut tanks of their damages, but for all the damage gutted from their kit, add base defensive stats and defensive scaling. For example, Sion's Q has ridiculous base damage, so, cut 30-50% of that base damage, and add 12 base Armor, 12 base Magic Resist, 100 base HP, and bump his scaling by 10-25%. Perhaps even add a new stat + a new item or two that adds some form of resistance to leath and pen. By gutting a Tank's damage, but bumping their defenses, they become "weak", this is true, but how do you counteract this? With their CC. Morg has a 5 year long root, so, bump the CC times on tanks, this adds in a effect of "oh, better kill the tank before they stop us from doing damage this fight." and makes tanks a actual target in a fight, rather than people just having the reaction of "oh, look, a bodyblock bot, better just CC it and move to the left."
"But whats gonna stop people from just targeting the damage dealers if tanks are just CC machines?" you might ask? A few small changes to tank items. For example, Change the Magic Damage from Sunfire, make it True damage, or the healing boost from visage, make it also spread healing to teammates if the the unit is already above a % of HP. Maybe add a tank item that has a short AOE taunt. These are simple solutions that make tanks much more viable at doing their job, as well as help in solving the "too much damage" meta everyone has been on about since the new runes came.
"but adding new effects or damage to tank items just brings the damage back." True, but in such a way that is healthier than "Oh, look, Mundo's Q just did 700 damage."