So I have tested lightning with various mages/staffs, mostly with lightning blade:
Wood staff +8= 1/10 stun
Chaotic +8= 1/10 stun
Elysium+8= 0/10 stun
Imirs made no difference to my stun. The above stun rate are not completely accurate, but approximate. Stun rate is about 10%. This is crap compared to ice, which is around 50-60% effective. This was done on a rogue with 55 LR.
TL/DR: Lightning in EUKO sucks.