The biggest problem was trying to not use other skills that weren't a part of the class my character was running. I had trouble with the two passive skills: weapon block and claw mastery, because everytime I attacked, I was naturally using them. That's why they are in the free class and also the exceptions to the rules. I found that the body class is the best to start with because you not only don't have to worry about the problem with the passive skills, but you can use the major martial arts skills as well. Other good classes to start with is either Pryokinesis or Electrokinesis, especially if you prefer to rely on you traps. A good second class to learn, especially if you took Body as your first class, is telepathy or shadow.
I developed the free class because there were certain skills that were useful, but also didn't fit in other classes or were going to be useful prior to the Izual quest where you could develope a second class. To resolve this, and make things relatively easier, the free class was developed.
As for choosing the Assassin as the character class, I noticed that there weren't many variants which focused solely on the Assassin. Also, I enjoy playing the Assassin a lot! So, she became the character.
Enjoy playing the variant.
Where there is no Honor in battle, there is no Glory!