Quests can now only be completed in Versus mode.
As someone who has spent a great deal of time playing the cooperative game mode, I appreciated that Heroes of the Storm treated that game mode as a valid choice. The MOBA genre is all about competitive PVP, so it's understandable that Heroes of the Storm would like to promote that aspect of the game, but the support for cooperative (PVE) play was a breath of fresh air. Personally, I wouldn't consider reducing the viability of playing Heroes of the Storm as a cooperative game a good thing.
You can find the full patch notes below.