1060 and 480 really really really really deserve to be on the same tier.
If you only consider dx11, then the 1060 almost deserves a tier higher, tho i dont know if id consider that tier. Really youd have the 480 at the lower end of the tier and the 1060 at the upper end.
If you only consider dx12/vulcan, then the 480 almost deserves a tier higher, tho again i wouldnt say its an entire tire. Now you have the 480 at the upper end of the tier, and the 1060 at the lower end.
On average tho, these 2 cards absolutely are on the same tier.
But taht leaves them in a wierd position, with all the old cards in their chart. Probably easiest way to do it is to create another tier for just thse 2 cards, below the 980/fury tier, above the next lower tier. That wont be right in all cases, but its the best i can think of to get the 2 newest cards from both companies compared correctly.