Gryzemuis

Are you sure ?

Haste does not only increase your white damage.
The extra swings will also increase proc chances of all kinds of procs.

Suppose I have slice&dice up at all times.
Suppose Blade Flurry and Abacus of Violent Odds are haste abilities I can enable at will.
I guess popping a haste potion is also a haste ability at will.
Suppose Mongoose and Thundering Skyfire Diamond are haste abilites that are enabled by a proc.

According to your rule of thumb, I should wait until Thundering Skyfire Diamond procs, and then I should enable BF and Abacus, and take a haste pot. That would give the highest increase in white damage.

Another way to look at this is: use your controllable haste to make the other proccable haste procs proc as soon as possible. (I'm sorry for the awkward sentence. )

I don't like to go full out at the beginning of a fight. So I will not use BF or Abacus during the first seconds of the fight. Say 10 seconds. During those 10 seconds, if Mongoose did not proc, I can enable BF to increase chances of Mongoose proccing. If Mongoose did proc, I will wait until Mongoose fades off, and then enable BF to try and make Mongoose proc asap again. Once Mongoose procs, I wait for it to wear off, and then use Abacus. Hopefully Mongoose will proc again. When it fades off for the second time, I can use a haste potion.

There are also the procs that have an internal cooldown. Or effects that don't stack. Using haste effects will increase the chance of a proc. But once it has procced, the cooldown/non-stacking will prevent it from proccing again during the short haste duration. If you spread out your haste effects over time, you might get more procs out of it over the full duration of a long fight.

The math is too complex for me to do this early in the morning.
But my point is: what gives more damage ? Multiplying all haste effects at the same time ? Or using haste to try to keep Mongoose up at all times ?