I've been reading some good things about Catacombs but I already have Micro Mutants: Evolution which I enjoy but don't get to play much perhaps because it runs a bit long. I know my son would love the DND theme so I am assuming it would be played more.
I own both games and enjoy them immensely. If you have the money I definitely recommend you get Catacombs. I like the theme of the game but it does take some imagination to picture the wooden discs as characters and monsters (the stickers on the discs help!) Even without the theme it is very satisfying to flick discs into each other! It has a different theme and action than Micro Mutants so besides them both being dexterity games they are very different. As for play time I would say it runs about the same time as Micro Mutants. Hope this helps!