Blizzard has just posted some hotfixes to Brann Bronzebeard including a more consistent baseline of power along with a 125% increase to his health and damage!
When this bug took effect, the higher the tier of Delve you were running, the stronger Brann would get.
We’ve just deployed a hotfix that will correct this bug. There should now be a consistent baseline of power for Brann, which will increase with your own gear and with his level.
Some specs, whose gameplay tended towards hanging back and letting Brann take the lead, were much more likely to trigger the bug than others, so for those players we understand that this could make Brann feel significantly weaker than he has been, especially in the highest tier delves.
We’ve also seen feedback that “unbugged”, Brann felt much less impactful than we’d hoped.