Joachim Trust not casting na spells.

Ok so i've noticed that while out there soloing my npc Joachim won't cast na spells on my WAR/DNC, i was skilling up the other day with Uragnites and i kept getting poisoned while i was within range he would cast poisona on koru and himself but completely ignore my WAR/DNC so i thought ok maybe it has to do something with the subjob but then i noticed a SAM/DNC not to far from me and his npc casted poisona on him, what the fudge! ? anyone having a similiar problem is there something i am missing or don't know from this npc? is he only not na WAR and only does it on certain jobs? or is mine just broken.