Honestly I don't remember which specials would reduce damage.... I know back in the "bows suck" era I was actually using a test client that I got from a Dev to try.... I was kinda an Archer advocate on the old Stratics. Heck my Stratics alias is even thanked in the Archer thread
I was doing TONS of testing... stuff like move and shoot etc. There was a bug that made you miss the first shot when you stopped. I was actually the one to discover and report it for fix.
If your shooting something a LOT and you have perfection and EOO and stuff going, you'll see an average of damages, then notice when a spell damage shot goes off. You'll get both damages, but the BASE shot will be reduced dramatically. They never did figure it out (or even get around to trying to figure it out). I'm thinking it was with all magical attacks with all weapons. Somehow it goes back to base damage without one side (the 100% from items, or the 300% from stuff) doing it's additional damage.
I *KNOW* that Frenzied WW was goofed up like this. The first thing you hit would take full damage then all the others would take damage as though you were using wrestling instead of a weapon.
