Yo, I’m new to Hearthstone so still haven’t completed all the solo adventures. I was playing the Boomsday mirror puzzle adventure, I got up to Astromancer Arwyn level 6 when I came across a seemingly impossible level. I kept trying to beat the level thinking of different strategies but nothing seemed to work. I finally gave up and looked up a tutorial. This is where I discovered the bug. The card Holy Smite was 2 damage in the video (1 year old) however, on my screen it was 3 damage. This buff to the spell makes the level impossible to beat as you need to turn a 4/5 to a 4/3. The only other cards you have are another Holy Smite, Divine Spirit (double a minions current health), The Stars Align (rearrange your minions by health) and your Mage hero power (heal 2 health) . Pretty sure I’m the only one who has discovered this, so like can I make my own custom Hearthstone card? 
Pick one, any one: https://us.forums.blizzard.com/en/hearthstone/search?q=boomsday%20category%3A8%20after%3A2020-03-21
Blizzard is aware, a fix is upcoming, ETA not announced anymore (fix was due between April 9 and 14, got delayed indefinitely).
So no custom card? 
According to another helpful player on these forums, the latest patch did include custom cards which appear to revers the previous card nerfs just for these adventures, but for some reason the full fix is not implemented yet: