They're referring to the demo, but complaining about things like "more luck than skill" and how it's "too hard"...
On a regular dungeon like library/crypt/snake pit/factory, you should be able to get somewhere above 85% win rate. It's not particularly hard. You just have to purposely use your class abilities as much as possible, make use of mid-fight leveling & always trying to kill the hardest thing you can instead of the easy stuff. Save pretty much all your potions for the bosses, too.
The bonus exp you get for fighting stuff stronger than you snowballs incredibly fast. From what I can tell, the bonus exp formula for each kill is (monsterlevel + leveldiff + leveldiff squared). For example, if you kill something 1 level higher than you, you'll get 2 bonus exp on top of the regular exp you get for killing it. The extreme example is when you're playing in the Factory and find Fireball early enough, you can kill a level 9 armor at level 1. He'll give you 9 + 8 + 8^2 exp. That's 81 exp, which is enough to put you to level 5 or 6 off of 1 fight.
Granted, sometimes you do get an unwinnable board but that's usually just 1 or 2 wasted minutes and it still leaves you with more gold than you had before in order to make the next attempt easier.
I'm currently trying to finish up the Boss Hive. Only 3 classes left (Changeling, Berserker, Fighter) The only "Argh!" places I've found in the game was with a Rogue in the Boss Hive (where meeting a vampire at level 1 is instant-death (because it takes 90% of your 5 HP and rounds up) or in Lothlorien (because it's designed to leave you at a severe disadvantage and you need to abuse either Cydestepp or Polymorph). As for the Gauntlet, I find that it's great fun. I'm up to level 15 on it... I feel like there's not too many classes that have a shot at beating it when it gets that high; mostly monk or vampire, I think.