I love Day9. I've been a subscriber for years. However, he's not a good Heathstone player. He makes massive mistakes almost every game. It doesn't look like he's actually trying to hard to focus on the game. Seems more like he's trying to be entertaining and blow of steam from working all day. Nothing wrong with that. It makes for a fun stream. It's just that it's not really great as a stream to learn from.
I recommend TrumpSC or Strifecro if you really want to get better. They're not nearly as entertaining though.