Some blades and some magic sounds like you might enjoy the Demon Hunters. I played and finished the game as one and it was good fun.
The Voodoo Pirate seemed too much like the Voodoo class recycled from Risen 2 and, well, the Mages (called Guardians in Risen 3) are the Mages just as you've seen them in previous PB games (there is some innovation, of course, but to me it looked too much like been there, done that).
The Demon Hunters are the least derivative of the three classes. There are some similarities to the New Camp (G1), Mercenaries (G2) but in terms of discipline and order also to the Old Camp and the Paladins though they pale in comparison to the strict rules of the Guardians. The DHs can also wield some magic. Not as much as the Guardians but decent enough.
Finally, their home world is the prettiest in my opinion and they are led by Eldric so it's a nice touch to be returning to one of the series' mentors.
You can't really go 'wrong' with any choice, of course. The game is easy as pie overall, even on hard, so you can really just pick the faction you think you'll enjoy the most.
Hint: If you want it extra easy and avoid the (IMO) unfun melee combat system, get a gun and some throwing knives early on. It will allow you to kill even the high level critters as a low level character. It's pretty ridiculous. You can take down huge golems with two shots from a pistol even as a level 1 character. That way you won't have to save too many areas for later. You can pretty much just waltz through everything with a gun until you join a faction and become more specialized.
Well, hope you have more fun with the game than I did. I thought the story was retarded, melee combat unfun and unbalanced (the game being way too easy in general) and I hated the shadowland parts that were just a horrible grind to me. The game generally has too much combat if you ask me... you can't go 10y in any direction without a fight. And the ending... well, you'll see
.
It had its moments though. The game is quite pretty on a whole, exploration is a lot of fun, and character development is surprisingly motivating
in spite of the unbalanced combat because it's just fun to get a shiny new skill or ability.
YMMV, of course, so just have at it and enjoy!