So I found this tier list online. It's too early to really make a tier list or tell what classes really succeed in PVP and of course it'll all change at max level and skill usually comes before class but here you go. Of course it's based off of the Asian versions of the game hince the female gunner and the thief class.
S Rank
A Rank
B Rank
C Rank
D Rank
I found this here http://www.kikosho.com/qt/wiki/index.php/DNF_Tier_List
And of course the tier list is player made but all are.
S Rank
- Rogue
- Spitfire [M/F]
- Mechanic [M/F]
A Rank
- Elemental Master
- Physical Exorcist
- Battle Mage
- Berserker (B → A 6/11/09)
- Necromancer (S → A 9/14/09)
B Rank
- Weapon Master [Large Sword/Club]
- Launcher [M/F]
- Infighter
- Nen Master
- Ranger [F]
- Magic Exorcist
- Soul Bringer
C Rank
- Weapon Master [Lightsword]
- Crusader
- Asura
- Ranger [M]
D Rank
- Grappler
- Street Fighter
- Striker
- Summoner
- Scholar (C → D)
I found this here http://www.kikosho.com/qt/wiki/index.php/DNF_Tier_List
And of course the tier list is player made but all are.