Hey Ruben,
I'll answer as much as I can
One of the reasons we are experimenting with the way card draw works is to standardize it across factions. The faction abilities that granted extra cards gave those specific factions what we considered to be an unfair advantage. The same can be said for cards within the decks that granted multiple card draws. Therefore we've lowered the card draw within the cards themselves and inserted it into the game rules instead.
Another reason is that if people had a bad mulligan they would often simply give up on the game as there would be very little chance to win. This isn't a good experience for the player or the opponent. For some specific factions, e.g. Monsters, this was even worse and more common due to muster cards and lack of card draw cards.
The decks within the stress test were purposely quite simplistic, this is why for example they include several pure value cards. We knew for many people it would be their first exposure to new changes within Gwent since the Witcher 3 and we didn't want the decks to be overwhelming, especially with the absence of a tutorial
From what you have played at Gamescom the cards as a whole have not been simplified. Something that might have caused some confusion is that Redanian Knights didn't use to be a pure value card, we exchanged them with another card that was. The total number of pure value cards available within each deck has actually been decreased on top of this.
Thank you for the feedback and if you have any other questions I will try to answer as best I can