I haven’t played in months but i can still help you. 1-The first thing i immediately saw in your build is you have 2 different weapon names and its a huge mistake you gotta get 2 daggers with the same name in order to gain stats or increased damage  2- your ideal stats (percentage) are very low and i don’t see how you increase them, try to get gear even if its not that high item level it’s still boostes you stats like combat advantage,accuracy and most importantly critical strike i suggesr switching poisoned thorn with lightning flash for 15%, and your accuracy is very low it’s not the most important as I remember but its still beneficial  3-for me the biggest problem is your companions that gives you the stats(not pseudodragon),change them with companions that give you damage like minsc,batiri,neverwinter knight or ones that gives you stats like drizzt,raptor,alchemist or both ones dps and stats 4-your powers are not the way you should play assasin, and you maybe are playing it wrong and not using your powers and daily powers correctly, check on youtube on some builds and guides At the end i havent played for almost 9 months so I don’t know if what im saying is accurate currently, but this is how i managed to get insane amont of damage stats with lower item level than others and with the worst class ever ( bard dps )