As a 15Nin/War with two of these and Wind Fans equipped:
12 procs over 106 hits, counting crit hits,and discounting misses and weapon skills, fighting easy prey.
Each proc consumes one Wind Fan.
So it's about a 10% (one in every ten) chance for wind damage. You see it as an En-Aero effect, and it shows up in the log as 'Additional effect: X points of damage.'
The wind damage ranges from 5-30, it's usually around the same as the Katana itself hit for, but occasionally higher or lower. Sometimes inflicts like, 30 damage after a strike for 21, so the damage really hurts when they go off.
They're excellent when soloing, I don't think they proc so often when I was fighting ITs in a party, but I wasn't counting then because I was concentrating on the fight- so take that with a pinch of salt.
Wind Fans can now be brought for ~20g in Whitegate (look up Wind Fan to find the vendors), and they stack to 99, so you can effectively use these katanas without spending a fortune on fans.
Edited, Feb 6th 2008 3:09pm by Nethesem
Edited, Feb 6th 2008 3:11pm by Nethesem