[scriby]

I think the branching factor is somewhat higher given that the order of actions makes a big difference. Also remember that when playing a card you have to choose where to place it, which can multiply the branching factor by up to 7.

If both of you have 3 minions on the board, each of your minions has a choice of 4 targets, which is already up to 4^3=64 choices. Then considering each order of attacks, and the fact that you can play any card of your hand before or after attacks, and the branching factor has the potential to explode.

[scrollaway]

For nearly all cases (except some you can specify manually and/or discover through deep learning), you can throw away positioning which is why I didn't mention it.

As for the order of actions, I did mention that. The basis of my argument is that you shouldn't consider an entire player's turn as a "turn"; instead, consider each action as a turn.