I'm having the same problem. Bought from all the traders. Won all the hero cards. Bought the white orchard stuff. Played until it won't let me win any more cards and yet I'm missing 2 or 3.
and maybe 1 more. Someone please help, it's all I have left to get the platinum.
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Iv done pretty much what you have while making sure i wouldnt get caught in glitches/bugs etc. im missing: Vrihedd cadet and Zoltan.. Damn this sucks, iv spent so much time chasing cards. hope they will fix it