We fully expect Blizzard to reveal more about all these features before the end of Blizzcon, but it certainly sounds like they are trying to correct some long-standing design errors that have hindered the growth of Heroes of the Storm.
Both characters were shown off in a stunning cinematic that debuted at BlizzCon 2017 that had them putted against each other with Alexstrasza taking her dragon form and laying waste to the surrounding area before Hanzo used his ultimate ability. If you aren't familiar with the character, she's a big part of WoW lore. Exactly how he's going to be implemented hasn't yet been revealed, but with previous Overwatch characters being introduced to Heroes of the Storm, we can make some good guesses. From Overwatch to World of Warcraft, all of Blizzard's adored properties have new surprises in store. On the field, Hanzo plays the role of a ranged assassin, which allows him to deal damage from a distance.
In addition, general improvements are coming to HotS in 2018, including "performance-based matchmaking", which takes into account individual match performances rather than just which team won or lost. However, you can get an early sneak peek at the new content when the developers release it on the game's Public Test Realm on November 20.