Definitely DK for both pve and pvp

Illusionist for pvp (only if the illusionist skills are working properly), it is hard to lvl a illusionist pve-wise. 

any class at high lvl can solo 90% of the bosses 

CB Knight = Mage = DE > DK=ELF > Prince > Illusionist

For some bosses, high lvl melee class is much better than mp dependent class especially CB Knight and DE.