I just recently ran a HOTDQ game, episode 2 with a lv 2 moon druid in my party. The druid was new to the game this week, and before even playing, he warned me that he thought he might be overpowered. I didn't think much of it at the time. Well, he was. Both encounters we had that day were basically made irrelevant by the druid. He just waded into combat with no worry of dying, because he knew the enemies couldn't deal enough damage to actually put him down. Now the party plan is to just send the "super bear" in to handle situations. Everyone at the table agreed he was overpowered, by far. Now, I'm faced with the option of either nerfing the class, or completely retooling the encounters in the published adventure to work around the druid.
It will work itself out. The Bear starts getting weaker and weaker. Nerfing or pumping up encounters will only make it harder on your party in the future. I played a Moon Druid and saw it fall off rapidly compared to other classes. Let the Druid shine at lvl 2 because it becomes less useful in combat as he levels.