Fyi, ninja=assassin...and clearly it's a ninja, where did the idea of theft come from? O_o;
Just don't know where SE is gonna put the role, dps or tank.
Why? Cuz' in ffxi, although ninja is a dps, but players were able to use it as a tank, which means there's potential in the skill sets. (utsusemi ftw)
At is end it really depends on how SE gonna define Ninja.

I personally would like to see the following, if possible.
Ninja, tank
Samurai, close dps
musketeer, range dps