Do Dungeons Require a Tank to Tank (vs. a Fighter/Tank)?

In Modern WoW, you “need” to be a tank specialization to effectively tank 5 man content. However, in Classic WoW, a damage dealing Warrior is actually a BETTER tank under some circumstances.

Is the goal with dungeons to fully require someone to be a Tank as their main class or can a Fighter with a Tank subclass tank?

Also, what is the most up to date guide?

I often find myself swapping between both roles in WoW (damage and tanking) and wanted to know if that is even possible in Ashes.

Thanks all!