I hate how the smithing tree is structured in general.
Why should my character need to learn how to craft Dwarven armour before being able to craft Orcish armour anyway?

From a roleplaying point of view, it makes little sense. The way it
should work, is if my character's overall smithing skill is high enough, he can learn Orcish smithing from an Orc blacksmith... or perhaps even from a book specific to Orcish smithing, without necessarily knowing how to make other types of armour.
As for weapon/armour stats... they're far too simple in my opinion. There should be more pros and cons for each type of weapon/armour, instead of one trumping another in every possible way. For instance with armour, some should be more durable than others; some (like chainmail) should allow the player to move more freely in combat; some should be better against different weapons, like defence against piercing blows, defence against crushing blows, etc. So the player has to consciously think which type of armour is best for their character in a certain situation... instead of simply working their way up an obvious pecking order.