Okay lets get cracking.
I’ve figured out another item needed for the ritual to open the portal to Camoran’s Paradise. The second item is the counterpart to the first: the blood of a Divine. This was a terrible puzzle to me. Unlike the Daedra Lords, the gods have no artifacts, and do not physically manifest themselves in our world. How then to obtain the blood of a god? But Jauffre solved it. The blood of Tiber Septim himself who became one of the Divines. This is a secret remembered only by the Blades, passed down from one Grandmaster to the next. Jauffre should tell it to you himself. - Martin
Let's assume the following to be true:
a. Daedric artefacts are made of Daedric blood.
b. Martin needs the blood of a Divine.
Then we have the following to examine:
1. Martin thinks no Divine artefacts exist.
2. Martin suggest that Divine artefacts are made of Divine blood.
These two assumptions are thrown together in this discussion.
Assumption #1 is a mistake on Martins side. Consider the Crusaders Armour, Dibella's brush, the Amulet of Kings, Boots of the Apostle and Lord's Mail.
At first glance assumption #2 makes sense because of the symmetry with the Daedric artefacts. Though considering that the whole world is a divine artefact, this gets a little bit tricky. A handful of dirt could have worked!
As an explanation. Martin might not have realized this, or Divine artefacts aren't made of Divine blood, or the world actually isn't a Divine artefact. I'm sure there are more. Which ever explanation is taken though. The blood (not the armour) of Talos is good.
So the explanation we're
actually looking for is, why no other artefacts are offered as a possibility. This is a question of
gameplay, rather then lore.
For plot, the the armour of Talos provides a nice excuse for Martin to change into battle gear for the coming scenes and for the player to visit a historically significant location. This fits in the overall pattern where development focuses on the highlights of Cyrodiil rather then the details.
While there are many Daedric artefacts, if the main quest is played from the start of the game, the only available Daedric quest is Azura's and this quest is strongly hinted at by the main quest. So basically we're looking at a desire to streamline the quests and their implementation. The Daedric artefacts were probably obvious enough, to warrant a branch, the Divine artefacts not so much.
Basically it comes down this: repeated generic fetch quests are boring and there for wrong.