I was wondering if it's possible just to solo parts of the DK's. Ive heard people solo Rex, but i don't know if this entails killing prime and supreme as well, or how exactly they go about it.

Usually when people solo rex, one of two things usually happen. They either get a friend to attack Prime and Supreme while the mage goes in so both of them don't attack the mage. The other option is for people with higher leveled stats, wherein they bring a melee weapon + a crossbow/crystal bow and kill the ranger then run deeper into the lair so the ranger can't see them, then they attack the mage. Usually they don't attack the mage after that. However on lower population worlds its probably better to kill Rex and the mager since spawn times are slow.

 

Its also possible to solo hybrid Prime and Supreme as well, however you need a mager for rex.

Check out my guide in beginning guides on soloing rex and supreme.