Next tank

[TouchandFeel]

That's true, when WoW heralded the swap from 6 MMORPG roles to just 3 (the thereafter-called "trinity" of roles) ...

The concept of the tank, healer, damage dealer trinity was primarily established in MMOs by the first Everquest, which was obviously way before WoW.
The roots of the trinity system comes from even before that, going back to archetypes that evolved in fantasy pen & paper RPGs like DnD. It's simply a reflection of the most common fantasy party setups of a big heavily armored fighter/knight character, a healer/priest/cleric and a long range but physically weaker damage dealer like a wizard.

WoW may have popularized MMOs in the West, but it certainly didn't invent anywhere near as many things for the genre as people seem to believe it did.

Here is an article from Game Developer magazine that talks some about the history and evolution of the trinity system as well the general pros/cons of it from a game development viewpoint as well as potential design alternatives or variants.
The pros/cons and general musings on how or how not to implement such a system are of course the opinions of the writer and I agree with some points while disagreeing with others, but the history part is accurate to my recollection.
https://www.gamedeveloper.com/design...-of-mmo-design