EDIT: So I reset my enhancements to see if that made any difference and I can now get improved critical on kamas and shortswords. However it still does not work on shuriken. (strangely though it shows different numbers on mouse over of the shuriken, even though it makes no difference when reading combat log) (was criting on a 19 and 20 but not an 18. standard shuriken with feat ICT and capstone should be criting on a 17-20 or 18-20 if no ICT feat) Resetting my racial enhancements still bugged out after i re-logged though....(thought i'd try it yet again..)
*Although also the halfling racial crit enhancer for thrown also doesn't work and I would guess its similar coding.*
EDIT: Tried resting my enhancements on my halfling to check again. Improved critical range from the halfling enhancement still does nothing when using shurikens.
Could the issue be something to do with the ranged side of the coding as it seems to be a common link?