Off the wall theory about the meta
This just occurred to me, so I'm sure it's flawed, but what if the jungle emphasized tanks over any other type of class. This would mean that tanks doing little to no damage (to champs) and being meat-shields would be less detrimental, and until we reached the mid-game they would only really farm the jungle and gank lanes where either items could close the damage gap, or laners could provide damage.
If tanks needing to do damage is the problem with a tank meta, then put the tanks in the jungle so they can have a tracker knife that gives them +500% damage to jungle monsters.