The Tabernacle is indeed strictly better and I will add one but it is also more vulnerable.
It's Legendary and as such I can play only one when at times you really want twice the effect to clean the board in a hurry or to really keep the board clear.
As a land it can be easily destroyed by a
Wasteland. It's much more difficult to get rid of
Pendrell Mists, especially when your land is tapped by a
Winter Orb.
Rishadan Port fits perfectly in an
Aether Vial build for example because you have your mana available to tap your opponents'. In this build I need my mana to develop my board position. Spending my mana to keep opposing mana tapped doesn't advance my own situation. And tapping two lands of my own to tap one of the opponent while under the Orb is not a good idea imo.
The
Vedalken Certarch actually perform the
Rishadan Port's job ... and more. Being able to tap lands, creatures and artifacts for free, for just one mana ... you can't ask for more.
Wastelands are not really necessary imo. I don't really want to destroy any lands, just keep the opponent from using his lands for a few turns while I go about unhindered.
Deck updated in opening post.
Thanks again for your input gentlemen. As always, my deck becomes better off it.