I found a bug. Well, that, or somethings wrong on my side, not sure.
Windfall deals way too much damage and is AoE. In burmecia, from backrow, basic attacks dealt about 114 damage, windfall over 500. About 800 on ironites(Who are weak to wind, I think)
I tried looking at the hws file, but as it used a number of unused things(effect is unused 114, it has the menu flags Unused(4) and Unused(5), I can't make heads or tails of that.
It still does the defence decrease(the line of text for the decreases appears at least).