I agree, that deciding which unit to activate is main part of taking decision. With random activation, is basically "race game". Your decision is vastly limited - which has pros and cons. Deck initiative is a good system to quickly test rules though , or to have friendly/fun/immersive/ non-competitive game.
another strong point of having card deck, is lack of needing to mark units with activated tokens. Which is a blessing. I dont use minitaures, but even im annoyed with the spoiled battlefiled by "Interface" elements.
and you can have deck of card in front of you, and choose which unit you activate. On the card there are all stats so its additional bonus of not having to check for unit stats.
you dont see this on photo, but i have 2x A4 papers with unit stat to my left - to know the stats of victim.
I think it could have been a cool thing to have sometimes. Another version is that you are allowed to place the cards in any order you wish before the turn starts and then the opponent may decide to move one or two cards to the bottom on your deck. And then you have at it. The activation order is set.
hmm...interesting. I think because i try staff like this before. that people would analize in her mind who will be moving when, which doesnt affect the game too much, but it "burn they mind". If the information is hidden, then its more relaxing.