I feel almost as bad when I get "pull it out of your ass" wins like that too. So many outcomes are obfuscated by RNG, it's really hard to tell where your skill is affecting the game. I can see on a macro level, my win rate has been improving recently, close to 5.5 wins per run, got my first 12 win run with an average rogue deck. But on a micro level, learning from singular choices is rare.
Also, fuck playing arena between brawls. Playing people at 2-2 and 3-2 that I would normally see much higher up the win bracket.