Ok, this was my working assumption, if its incorrect then that will answer some things:

I assumed that everyone in the party got credit for everyone's contribution.

However, my wife and I are in a 2 person party. I'm a 34 Paladin. She's a 34 Scholar.

We do a Fate. We both get gold I get 12,000+ xp, she gets 8,000ish XP.

Ok, we both got Gold, how is that possible (is my first question).

Then, we go to a fate and she and I are the only 2 players in it. Takes 15 minutes, but we clear it.

I get 12,000 xp she gets 8,000 XP.

She changes classes, changes back. We go to a 3rd FATE.

Again, I get 12,000 xp she gets 8,000.

Anyone have any insight as to why we are both getting gold but getting 2 different xp amounts at the same level?