From Ben Hayes:

One of the biggest challenges with developing Commander 2016 was making the mana base and color fixing in each deck work smoothly.

While it’s normally a goal in products like this to cycle out cards of this type where possible. As the lead of Commander 2016 development, I made the call early on that prioritizing that goal highly would be too detrimental to the overall experience, and the playability of each deck.

Different strategies and especially different suites of gold cards demand different types of lands of a deck, so the suite of mana fixing lands you see in each of the decks is the composition that I and the person responsible for the development of that deck thought was the best it could be for that deck, without being concerned with the goal of cycling everything out if it didn’t make for a better final product.

Below are the rare dual lands you’ll see in Commander 2016!

Enjoy!