Tanks should have more active durability at the expense of passive durability

They would be healthier for the game, RIOT could afford to make them strong as a class without also making marksmen feel comparatively weak as a class, we could make their high and low moments have higher contrast and differentiate them from bruisers, and they would be more rewarding to play and master.

They should be less durable passively (through bonus armor and bonus health) than they are now, though still have higher passive durability than other classes, and their items should provide slight passive durability boosts and really focus on temporary boosts to their durability that allow them to function as juggernaughts in team fights.

The effectiveness of the items should be gated to scale with armor and health, making them much more effective on champions that stack tank itemization rather than those that dabble in it.

The active durability ought to make the tank damn near impossible to kill for the first half of the team fight regardless of how much focus fire he withstands. The natural counter to a tank should be strong disengage because the cooldown on the active durability would focus him to play a more timid role if the engage was unsuccessful.

An assassin should be able to threaten a tank that is roaming around in the jungle, and although not necessarily kill the tank, atleast force him to use an active and make a window for his team to play on.

If it comes down to a fight between a tank and any damage dealer, whether sustained or burst, a tank with all his actives going ought to be unassailable. The counterplay should be time and knowing when to fight and when not to fight, not "just focus him". The whole point of playing a tank is to absorb focus fire.

Windows of high moments and low moments are more interesting to play around and with than a strictly passive increase in durability, the same way ghostblade active and temporary steroids like kogmaw bioarcane barrage or intermittent nukes like shiv are more interesting to play around and with than a strictly passive increase in damage like phantom dancer.

Here are some example actives:

• a shield equal to your bonus health, lasts for 3 seconds + 1 second for every 50 bonus armor.
• flat damage block equal to your magic resist for 1 seconds + 1.5 second for every 1000 bonus health.
• damage reduction versus area of effect equal to the higher of your physical damage mitigation or magic damage mitigation for 1 second + 2.5 seconds for every 1000 bonus health.