The plight of the early-game tank
The way I see it, one of the big issues with tanks versus... anyone else, really, is their lack of early game presence. While, yes, the early game is rather irrelevant (Levels 1-4) and this rarely comes up unless one side or the other is hyper aggressive, I think it's a problem that should be addressed.
Tanks start off on virtually the same level as everyone else in regards to health, armor, and magic resist. Nautilus, for example, at level 0 has 1 more armor than Miss Fortune with .25 more growth per level and 3 LESS HP with +1 more growth per level. For being a tank, he has slightly LESS durability than Miss Fortune at level 1 while she's vastly stronger. I feel this should be changed, because if the enemy decides to get stupid aggressive, assassins and ADCs get a huge advantage over the tanks, who naturally have little offensive capability and don't provide as effective a retaliation. Ultimately tanks get most of their defensive capability through items, especially early on, and their natural tankiness scale up roughly equal to everyone else.
My proposal is to give tanks higher starting health, armor and magic resist while reducing their stat growth per level. Ideally, this should give aggressive carries and assassins greater pause before attacking and counterjungling, or take more effort to bully tanks out of the lane, as they have to fight a hardier opponent, and in regards to jungling, will take longer and increase the likelihood of neighboring lanes coming to the rescue. A possible downside is this will make tanks TOO imposing early on (specifically ones that can lunge or grab, namely Leona, Blitz, Thresh and Nautilus) and reverse the current roles of damage-heavy champions bullying everyone.
Whatever the outcome may be, there is a very present problem with tanks being remarkably and ironically squishy early on that I feel needs to be addressed.