Keep in mind that any crafted armor can have its class-restriction removed with the right material, like Snoufleur for Medium armors. So the question is really, what is the best armor, period?
The Skin That Strikes armor is good even by itself, but of course if you are going for the full Taken Shape set, it's a must.
The Qunari armors are pretty (on the right race/gender combinations -- do not put the Superb Antaam-saar on Solas, unless you want to go blind), but they aren't that great stats-wise. Some of the Avvar armors also look good, but again, not that great stats-wise.
I don't much care for the Descent armors. They are ugly as sin, can't be upgraded, and don't really compensate with enough OP buffs to be worth it.
I like the look and stats of the Dragon Hunter armors, but they are not upgradable. I only use them when my characters are level capped and armor kind of doesn't matter any more.
There are special situations where a Medium Armor is actually best for all classes, including Warriors. My current Level 22 party rocks the Superb Prowler Armor, crammed with Dexterity and Cunning buffs. Even the warriors and mages. Look at how good they look, and their stats are awesome:

Before the DLCs came out, the Superb Prowler Armor was hands down the best armor. Now with a few more choices, your mileage may vary and I may try one of the others mentioned above for a while, but I still end up going back to the classic best.