This is a tricky encounter but raw aggression can win the day nevertheless. Since the two Paladin buddies keep swapping back and forth, no extra health is applied to the Heroic version of this encounter. They do start with three mana to make things more challenging, but otherwise the same rules apply as they did in the story mode: if you kill one of them, the High Five! cards get automatically discarded, and your turn doesn’t end at that point, meaning you can still attack with any leftover minions you have.
Since Paladins struggle with early aggression and wide boards, we opted for an Aggro Warrior build with many of the new Adventure cards to take them down: once you build a wide enough board, neither George nor Karl will have a reasonable answer to stop you. Fun fact: the AI will miss lethal with the Golden Blade hero power – though hopefully your battle won’t come to that point!