[SixOfSpades]

I agree, this is a ToB topic. But since I can't move it and I can answer the question:

Given: A character with 2 attacks per round in their on-hand weapon (let's say it's Cutthroat), holding Kundane in their offhand.

A normal round: Cutthroat, Cutthroat, Cutthroat, Kundane. (4)

Under Haste: Cutthroat, Cutthroat, Cutthroat, Cutthroat, Kundane. (5)

Under Improved Haste: Cutthroat, Cutthroat, Cutthroat, Kundane, Cutthroat, Cutthroat, Cutthroat, Kundane. (8)

Under Whirlwind: Cutthroat, Cutthroat, Cutthroat, Cutthroat, Kundane, Cutthroat, Cutthroat, Cutthroat, Cutthroat, Kundane. (10)

Unequipping Kundane prior to Whirlwinding would result in 10 attacks with Cutthroat alone, and result in more Critical Hits if the person has points in Single Weapon Style.