I honestly think you have difficulty reading. To be a tank you need to be able to redirect damage towards yourself so that other players do not receive damage which allows them to do damage. Only one class in the game can redirect damage because they have an Aggro pull that forces monsters to attack them.
Going further, because of this any class outside of this can still pull a mob, they just canāt ensure that it attacks only them unless they are dealing the most damage to it. Maximizing damage however also generally means less CON which makes you squishy. However Any class can slot CON conceptually and most will. Itās not an issue of health as anyone can have high health but of sticking power which only a Peltasta guarantees you.
Keep beating this bush when out of 4 base classes there are 12 paths at C2. 1/12 can tank. By Rank 3 there are even more class paths, and only 2 of those multiple paths can tank (Taking either Pel c2 or taking Pel C1 at rank 3). Thereās no realistic ratio of tanks to any other archetype in this game, you canāt ensure one and the game does not necessitate one.
You donāt need a tank for any dungeon, outside of Earth Tower.