I'm not sure why you think Shadowheart would have more AC than a knight ranger. If you go for heavy armour you should probably go for a shield too and skip two-weapon fighting. Take Dueling Style at second level instead, it works with shields.
Also it hurts me to call the "favoured enemy" options "subclass". They're not subclasses, they're class features in same vein as fighting styles. Pardon me if I'm being too nitpicky, but let's try to keep the nomenclature clears.
