1% per level of the character. Proc lasts long enough at 36th lvl for 2 backstabs. Usually procs 2 times a combat. I am using it in my off hand with a Slime coated harpoon in the primary and yes the haste effects all forms of combat. This is also one of the best looking weapons in the game as it looks like a nice shiney Katana. Picked is up off of the "Gladiator" class giants in Kael. Do not expect to waltz in and farm this puppy even if you are 60th lvl. I am willing to trade this if the offer is right as it doesn't belong on a twink, but I needed to test it out myself.
Baretta
lvl 36 rogue
Inny Server