Note: All credit regarding this information leak goes to XOF.
Among these, are cards owned by the protagonist Jaden Yuki and other prominent characters such as Aster Phoenix, Chazz Princeton, Alexis Rhodes and Bastion Misawa, meaning that they might be the first unlockable characters once GX is added. The datamine also shows the rarity of some cards and how duelists could get them.
Zane is a powerful duelist from GX series, his deck is themed around Cyber Dragon and it's other forms and fusions, his deck then centered around both Cyber Dragon and Cyberdark later on in the series.
actually, I remember a version of the anime where Chazz DID use L&D Dragon, but for some reason, that part of the anime can't be found. It's the same thing with the planet card series (Terra Firma is a part of it.) There was an entire story arc with the planet card series, but when I looked back to re-watched the series, it wasn't there. My guess is because it was produced by 4KIDS
IMO the biggest issue is the cards. So many GX anime cards are either very underpowered compared to the meta cards at that time, or are actually good but have unneeded restriction slapped on them when they are printed in real life, or printed without enough support, whether from anime or game original.
Also arc V introduced good cards, although the anime itself was moronic and lazy. yuya just "action card" everything to get out of situations. That's just lazy script writing for writers who can't be bothered coming up with original ideas for their duels.
But arc v did introduce alot of good cards/archtypes.