It looks good. A ton of similarities to Diablo 3's classes and skills. The most unique is the arcana which is a wizard/gambit hybrid though Gambit wishes he was as cool. Definitely going to be my first character. The battle master is a monk. The devil hunter is, yup you guessed it, a demon hunter but uses swappable guns (pistols, blunderbusses, and a rifle).
The effects look pretty fantastic and over the top. Even the very similar skills have some extra oomph to them. For example: D3 would have a glowing orb with a wire of lightning around it and the Lost Ark counter part has 3-5 lightning wires and leaves a trail.
They even implemented the rune system from D3 but it acts like the old system where you apply up to 3 types of runes (element, firing style, and aoe type). It looks like they are unlocks that you earn rather than looted components which is convenient.
Skills are combo/charge focused. So they seem a little more potent but also more plodding. Hopefully they will get the combat pacing right though it seems like it borrows a page from Dynasty Warriors with its legions of swarming/charging fodder that can be brain dead. In D3 you have to make some effort to herd the maximum amount of foes into your big kablooey skill. In Lost Ark, like DW, it looks like a lot of the herding is done for you.