Newer Update: I seem to see the same CARDS being dropped at the samer locations but not always the same Moga dropping the card, so I am beginning to believe it is a function of locality rather than the Moga you are fighting. Perhaps both though. Too early to be sure.
I'm not sure if this matters or not, but I fought Trollo 5 times at the bridge and he never dropped any card at all, I also believe it's probably the location that determines the cards dropped, but perhaps some mogas drop cards at all at some locations, and some don't? Just a interesting little side note smile
To be frank, I just feel that they just give out random cards, no matter what location or Moga you fight.
However, I wish you luck on trying to figure out the pattern of the cards. If it helps, I don't remember what sort of cards I have, but it seems I have mostly Scorpio-Rare cards at Sitnalta Plaza while I was doing my Black Gold quest.
I agree though they randomly give the card and it isn't correlated with the moga that we fight or the location
recently found a Gryph card from a Trolo on Oakford Shade, I'll try to keep track of any other ones i find 3nodding
And I have also noticed that there the cards seemed to be grouped by location, the Moga that drop them however are normally random (And by location I mean general chunk of area, like the woods being from Shadowmire Edge to Oakford Shade, etc.).
Good Luck cracking their "random" drop ninja
umbranine... peascorp... darkwood... common... leo (this card took a while to get, the final card of the set for me. having trouble finding yugure, munyu, yoake, willo, cathulu & Jor to complete 6 other sets)