The new Slaveforged Guardian heavy armor currently gives grit. While I understand there might be gameplay reasons for this, such as balancing how many armors of each type provide what attribute, I don’t think this is the right choice.
On the developer stream preceding Isle of Siptah (the recap of which can be found here: Developer Stream Recap: September 11, 2020), it was said that the Guardian armor was meant to be aggressive in its design, as evidenced by the sharp angles and pointy ends of the armor. Strength is much better suited to such a design, being the stat most closely analogous with aggression; you of course use stamina to attack, but the stat as a whole is much more about endurance, which is why only one of its bonuses has anything to do with attacking.