First of all i am not an expert but i have experience GX and based on my experience:
1.) Rolling cutter is a Mob killer skill but can't even mob greatly because of Mob flee penalty effect.
2.) Ok, so you can't mob with RC then use Weapon Blocking skill to increase defense when mobbing...[WRONG!!!]...Weapon blocking is so retarded that when used you can't move at all for a few seconds and only 20% chance at 5th level.
3.) Oh man i am poor i can't afford expensive items...oh i know! ill use Poisonous weapon and craft New poisons with new poison research skill to increase my damage!...[WRONG AGAIN!!!] Poisonous weapon doesn't even do anything as far as i experienced it all it does, no i am wrong, it doesn't do anything...it doesn't even make your weapon poison type when used...why is it even called poisonous weapon????really???
4.) Ok so you say you can't move with Weapon blocking and activated, then why don't you use Dark illusion skill so you can reach those long range mobs?......[WRONG AGAIN!!!!] When you use Dark illusion skill there is another downside on it, you can't use skills for a few seconds when dark illusion is used coz of delayed cast effect.
ENOUGH SAID, GX is retarded...specially Rolling cutter PFFFT but anyway Good luck on poor people who started as an assassin class (LIke me) All i can farm with my GX is Arc angeling and have to be buffed with "Enchant deadly poison" before being able to kill it....