Hearthpwn

There a few ways to get creative and change the card, depending on which interaction you want killed. The easiest way to kill the brann interaction would just be to get rid off all the battlecries and make them manathirsts. Does make the cards weaker to play on curve, but shrug.
As for shadowstep, that is a lot harder to kill. You could try something like making the 8 mana one have Manathirst 10: Deal another 8 damage and Astalor dies. That only stops them from shadowstepping the final form, through. You could buff them all by giving each form Can't be targeted by spells, also finally keyword that to Elusive or Shroud or anything.
You could make all of them neutral spells, like sunwell, that summon the bodies as vanilla minions. That would destroy all those interactions and open a few new ones, such as the shaman quest and mage owl and that other legendary. More of a sideways move, I suppose.