So I've read that you max out int but you don't really have much survivability and very party reliant.
As to build a throwing Assassin, it is much advised to not start out with a throw build at first on the occasion that your damage per second would be low, you would have low survivalability, evasion, HP, etc.
How I would build a throwing Assassin, from my perspective, is to go AGI CRT with nail or special bow weapons first. This allows me to have a high survivalability through evasion and a decent damage per second, even though I am not utilizing the weapon mastery...except for bow. Around building on AGI CRT, I would have some VIT, about 50...not exceeding 50, as it would be too much...not focusing on damage potential but defensive potential, in which Assassins have a low base HP but high base EVA. A 50 VIT is good to survive a couple of hits.
At the beginning, it is advised to build AGI to 140 at a low level to build up to max ASPD for nail weapons and to provide some decent damage. As for bow, I think not it would reach max ASPD at that value, but the "Evasion" skill would cover for that, along with a "hidden stat increase" for each time you scale up higher in the class tree. After getting to 140 AGI, it is advised to then go for 210 CRT, to build up higher, the damage of critical and its rate and accuracy, as critical hits never miss. After reaching 210 CRT, build up on your AGI to max value, 256, to ensure high evasive ability and high base damage with nail and special bow weapons. After maxing out the AGI, max CRT to 256, to ensure higher critical damage multiplier and rate and higher double attack trigger. For level 3 double attack, it takes 9 CRT values to raise the double attack 3 trigger chance by 1%. At 210 CRT, you have a 34% double attack trigger chance and a 75% critical attack chance. At 256 CRT, one would have a 40% double attack 3 chance and a 90% critical attack chance. NOTE that critical chance cannot exceed 95% in value.
Oh, forgot, AGI rises the base attack by a value of 2 when wielding nail weapons and a value of 2.5 for special bow. CRT rises the base attack by a value of 1 when equipped with a special bow.
After maxing out both AGI and CRT, which is at around level 168, aim for 50 VIT, which would be achieved at level 184. After that, build on the STR value if using nail or DEX if using special bow.
The reason for the AGI/CRT build is to allow a bit of survivalability and to level a bit faster, as a backstab Assassin would, even though they pose a higher damage per second, MP drains rather quickly when one is at a low level - meaning one would have to hoard up o MP potions.
At around level 200, I would advise to finally restat to backstab Assassin. In my opinion and viewpoint on how to redistribute the stat points, I would work backwards, maxing CRT first for the critical damage and rate, in which at 256 CRT, backstab has a 33.4% chance of triggering a critical hit, or for some other people, "a double backstab". Although a 33.4% critical hit chance for backstab is quite low, it can be corrected by wielding a throwing weapon with a "+30 Critical Rate" status to increase the chance to 66.4%. Next, would be DEX - max that out, to increase a bit of damage (for throwing weapons) and to reduce the skill delay by about 6 to 6.5 seconds, as per 20 DEX is -.5 seconds in skill delay for backstab, not other skills, in which 256 DEX is a reduced 1 second skill delay. After maxing DEX, pour all stat points into INT to further increase the damage.
By that time, one would drop the nail and/or special bow weapons and utilize throwing weapons, to increase backstab multiplier damage and to utilize the throwing weapon mastery Assassins have.
This build, has a high magic evasive potential, but a bit of a low physical evasion.
There is, however, another build that utilizes the Assassin's high quality evasion. One would build as AGI/CRT/INT - AGI for physical evasion, INT for magic evasion and to increase base damage when equipping throw weapons, and CRT for damage. Like before, restat to this build, if desired, at around level 200 or more to have a bit higher potential with this build. Maximize AGI and CRT first, to utilize the damage and then INT after maximizing both. One could utilize nail weapons with this build at first, but later on in the future, when INT could be built high enough, throw has a higher potential.
With the AGI/CRT/INT build, Assassins have a skill, which is like a counterattack - when evading a physical hit, there is a chance to counter attack in return, with a possibility of triggering critical damage in return. The skill can be acquired at level 200 in Spargas Harbor's Butterfly Rainbow Bar. The skill goes by the name of "スキア" in Japanese servers.
You can follow this on your own volition...although you can build however you want it to be as...I'm not the one to force you to follow this mini-guide. 
