Ok you farmed all the way to 375 favor and according to ddowiki you can choose only some upgrading options for certain armors.
For example it states Goristro: "can be made part of the Woodsman's Guile set with 375 purple dragon knight favor"
but what if I consider the light armored toon should be PDK set. Looks like I wont have that option.
Taking into account the effort that it takes to get 375 favor and that D&D is about having options and not limiting options (that's other rpgs territory) why shouldn't we be able to choose to make it part of any set.
Likewise with the other armors...
Tier 1 should allow you to upgrade the armours as we have now with tier 3.