This happened on duels with the DH hero, so not sure if the bug also happens on constructed. I ran the Lion’s Frenzy weapon to do a draw heavy build but the weapon did not seem to add its attack to my hero’s attack. Despite my weapon having 4 attack at one moment, the game wouldn’t let me strike. Only when I added attack to my own hero through the momentum spell would it let me, and the attack numbers from the hero and the weapon were shown separately, as if decoupled somehow.
This only happened once, since I just abandoned the run altogether after the loss, so not sure if it was a one off, but the bug is surely there. Hope this helps sorting that out 