Taken by the Korean media, I apologize for the shaky and blur camera footage. If anything, it can be seen that Mabinogi II:Arena is certainly leaning towards more of Mabinogi Heroes than Mabinogi at this point of time with the instanced-based dungeon action combat. But still, Nexon has yet to reveal what players can do outside of combat, perhaps those features are saved for later.
4 characters classes were available for testing, including the Archer, Bard, Heavy Hammer and Sword + Shield (the latter both are melee warriors). Korean media ThisIsGame has uploaded footage of all 4 of them, so have a look!