Paddy Fitzpatrick
If cleric heals were buffed then real tanking could become a thing, or at least you could have a primary and secondary tank. If shields added bonuses to resistance or defenses then again, tanking could be a thing. If heavy armor offered more than just physical resistance tanking could be a thing.

Right now, there is no way you can get tanking from any class in the way the term is understood in traditional MMOs.
Departing from the idea of the tank/heal/dps trinity of traditional MMO loops was a design goal.

The PvE paradigm that I think will end up working best will be a group of PCs that split the mobs between them such that everyone has resistances, defenses, damage types, and targeted defenses that compare favorably with their direct opponents. The heavy armor physical weapon fighters would tackle the lightly armored physical weapon enemies, the heavy armor Energy damage PCs pair off against the heavy armor physical damage mobs, and so forth. Control and buffs flow where needed from where they are available.

PvP is a bit more complicated because manipulating intelligent opponents tactics is much harder.