Considering that I enjoyed 10,000,000 to a fair degree, I had reasonably high expectations when I heard Dungeon Hearts was a mixture of puzzle and role playing games as well. Much to my disappointment, I instead found myself bored to death within 20 minutes of starting.
My biggest gripe with Dungeon Hearts overall is that the RPG elements feel very tacked-on and unnecessary. Character skills are poorly explained and feel clumsy to use due to generally poor interface design. Above all, there's very little feeling of actual progression and very little done to break the general monotony of the gameplay. Every enemy is fought in more or less the exact same manner - form attacks by combining 3 of the same color piece, move the attack gem onto a line that contains an enemy attack gem, and click. Repeat ad infinitum. Combined with the total lack of story, the "epic journey" feels like little more than a slight occasional change in backdrop scenery.
When you strip away the façade of supposed RPG gameplay in Dungeon Hearts, what remains is the puzzle game aspects. Unfortunately, as stated before, the puzzle game core is incredibly repetitive and comes with a click-and-drag system that feels incredibly choppy and awkward to use. In the end, the only redeeming factor to be found is the surprisingly solid soundtrack.
In summary, Dungeon Hearts pretends to be a unique blend of the classic "match-3" puzzle type game and an RPG, but at the end of the day, the RPG aspects are little more than a shallow veneer coating an even shallower game.