I like it! Especially the arena.
Arena feels balanced and very replayable (played two games deep).
With the dungeons I couldn't beat the initial swamp without getting booster packs (and after getting them it became too easy). But I was still getting the hang of the mechanics, so maybe that's why.
The open-ended design of the overworld confused me a bit, not sure why should I go to one location over another.
It would be nice to have a way to visually determine if the minion attacked already.
Overall very good!
Two bugs I've encountered:
1. In the arena the card pool doesn't reset on returning to the main menu, but the deck does.
2. Lots of taunt popups in the lobby between arena battle (an empty card prefab?)