With regards to the PAX version of Tafari and the regular version being used in the same deck - this is a horrible, horrible idea! In a competitive game there should be no bonuses for receiving limited edition or "special" cards other then their own cool factor and uniqueness. To draw a comparison with Magic: The Gathering; if having a special edition of a card allowed for having the special version and the original card in the deck, I would imagine the Magic competitive scene would fall apart. MTG and other card games treat any promo or special cards as effectively regular versions of the cards, just as they should!
In fact I would go so far as to say that having this PAX version be used in addition to the regular Tafari would be going against some of the core ideas that Sirlin had when he envisioned the game.
"These cards are functionaly equivalent for gameplay, but they allow collectors to have something cool to collect (namely the limited edition black bordered cards)."
Disagree? Please tell me why. I feel that even if having two Tafaris is not overpowered it is still an advantage given to PAX attendees.