Playing a Battleground match with Deathwing, I realized that it looks like something’s wrong. All the minions get +2 attack at the beginning of the round, this thing is working. But I am playing with Dragons, and I have a Whelp Smuggler ( after a friendly dragon gains Attack, give it +2 health ) and looks like it’s effect is not triggered by Deathwing’s passive.
More specific - had a Whelp Smuggler and a Bronze Sandspewer. At the beginning of each round, the dragon got +2 attack thanks to the Deathwing’s passive, but didn’t get +1 health from the Whelp Smuggler.