Woulden't that mean Talos is just an avatar of Shor/Lorkhan and shoulden't be a new divine?

Yup. He's the "new" Lorkhan and replaced him in the pantheon, though that's still a gross oversimplification of Talos' divinity and mythical role.

Essentially, Talos' was so good at mimicing Lorkhan that the two became indistinguishable, the only difference being that Talos ain't a "missing" god like Lorkhan/Shezzar is, which is why Talos is considered a "new" divine.

Oh yeah because Talos mantled (?) Lorkhan

The three guys that make up Talos mantled* Lorkhan.

Mounting Lorkhan would be the title of a story too inappropriate for these forums.

Sorry I mixed up Lorkhan and Talos for Vivec and Molag Bal....