The newest Heroes of the Storm comic has arrived that very obviously ties in to the World of Warcraft faction struggle coming in Battle for Azeroth. Interestingly, the WoW pre-patch event is called War of Thorns and one of the central characters in the comic is the Lady of Thorns, a character seemingly on the side of "good" in the Nexus. She alludes to one of the "Nexus realms" being in danger of falling to the Raven Lord's "evil".
The "Secrets of the Storm" comic begins with Deckard Cain meeting a new character named Orphea who speaks of how realms die through "chaos, destruction and war". She shows Cain the Dark Nexus controlled by the Raven Lord that he calls "such evil" and calls for "someone to stop them".
Interestingly, when they go to the Lady of Thorns in Dragon Shire, she speaks of her husband who has been turned to stone and that she is also cursed. Orphea shows the Lady a shard from "another realm the Raven Lord wants even more" that has just formed. They decide to try to stop the fall with Cain contacting his allies, namely WoW Alliance characters such as Malfurion, Tyrande, Uther, Jaina and other Blizzard characters dressed in Alliance-themed gear like Johanna and Auriel.
They march off to battle and, in the final panel, face off against the Raven Lord's forces in Alterac Pass (the newest HotS map) that carry Horde banners and led by Drek'Thar.
Is the "realm that has just formed" that the Raven Lord wants control of Azeroth from World of Warcraft? We'll have to see in later comics!
Check out the comic on the Heroes of the Storm site.