We've gone through a few sessions of this now, having just gotten the game for my daughter's birthday (full disclosure: I'm a "real" D&D player going back 30+ years now). We've not played enough iterations to really decide if one class is wholly underpowered, though so far we are tending to think it is the rogue. We have already made one house rule change involving them, and will likely make one more.
First, the idea that you are supposed to honestly remember all of the secret doors is a little tough for us, so we have already decided that you must roll each time you try to cross a secret door, unless forced through one because of combat. We are also toying with the idea of making the secret doors card move regular players to rogue level and rogues are the only ones who get auto-find. This would help balance those pesky cards a little bit.
The second change we are considering in the rogue area is to add a sneak ability. If a rogue enters a room or chamber with a monster and there is a door or passage on the other side, the rogue can sneak through and move past if they roll a 4+. If not, they must fight. This would improve their mobility a LOT and might compensate for their very weak combat some. Imagine this - they see a stronger character go down in a deeper level, and zip over there to attempt to claim the loot.
As an aside, I'm also liking the suggestion made to allow rogues to double wield swords. In the games we've played so far, rogues have a pretty hard time of it if anyone else decides to raid those level 1 rooms, and they definitely are in trouble going any deeper than level 1 without a magic sword. Given that they would already have a hard time trying to GET two swords, this doesn't seem like a common occurrence for them.