You can wear whatever you'd like. That doesn't change the fact that heavy armor is for warriors, medium armor is for rogues, and light armor is for mages. That has always been the case for every Dragon Age game. With that understood, you are more than within your right to craft and build whatever type of hybrid you'd like. I'm just asserting that heavy armor by definition is a tank gear set. You don't have to necessarily be a tank to wear it.
Anyone can wear plate in this game. Or heavy armor, whatever you want to call it.
And yeah, as you can imagine, Warriors are not the sole tanks in this game.
I'll give you that all Warrior specs can tank however, while Mages need to go for KE.
By the way, we know that Warriors can go all Conan if they want, run around in furs and whatever. You can use schematics anyway. They said this one year ago, along with classes having more crossovers than before. It's a good thing imo.
Tanking can work in a lot of ways. There is block and mitigation tanking, evasion or avoidance tanking, magic mitigation through shields barriers and protections tanking, etc.
On topic now, sexy armor doesn't work obviously, but in a fantasy game? Yeah do whatever you want. Just don't restrict people into using only sexy armor for females f.e.