Clarification on the tank problem

For a long time now people have been complaining that tanks are useless or underpowered or get oneshot. There have been a lot of discussions on how to fix this with several tweaks to %pen or new item suggestions. I am not a developer or anything like it so I am most likely not able to see the big picture and I would like some members of the riot balance team to help me with this but until then I can provide some corrections and guidelines on what tanks need, want, and what effect it will have on other roles.

To start of let me define what a tank is (at least for the purpose of this thread) since a lot of people are misusing the term (this includes lcs casters i would argue). A tank is someone who contributes in teamfights by using crowd control on assassins and bruiser to peel for his own carries. Other than this a tank provides utility and while he can provide initiation it is not required by any means and in some cases obstructs him from effectively teamfighting and peeling after the initiation is over. You can effectively say that a tank is a second support which is why almost all of them function well in the support role only hindered by possible weak lane.

This definition is in contrast to a "tanky" characters. Anyone can be tanky heck you can build talon tanky but that does not make him a tank. Same thing applies for what lcs casters so nicely dubbed "disruption tanks" (mundo, shyvanna) which are not tanks but in reality is closer to insanely tanky bruiser with less kill potential than traditional bruisers (irelia, jax).

Now with that out of the way I would argue that a tank despite their name only needs enough survivability to last through their initiation, if they have one, and any residual aoe damage. The moment bruisers and assassins completely ignore you is the moment you have too little utility compared to tankyness. Optimally any enemy divers are faced with the option to kill you first while they get killed by your carry or try to kill your carry but get locked down by your utility/cc and still get killed by your carries.

I write this as a contrast to people saying that tanks are not tanky enough which simply is not true. Sure they can get focused down in under 5 seconds by an adc but not by an assassin/bruiser. What tanks need is more utility like the one frozen heart or locket of the iron solari gives you.

Now i want to hear your opinions and i will edit them in here in the opening post if they are popular and discuss what effects they will have on the game.