Are there diminishing return for crowd control

Both of the links you provide say "Stacks in duration". According to the Effect Stacking page

Effects stack in one of two ways: in intensity or in duration. For example, multiple stacks of bleeding, which stacks in intensity, increase the damage dealt over time, and multiple stacks of regeneration, which stacks in duration, increase the duration that the healing over time lasts.

It also says

The best intensity lasts for the cumulative duration

Originally I interpreted this to say higher damage trumps lesser damage but increases duration which is incorrect. Based on info I found at Guild Wars Insider the answer becomes a little more complicated.

Multiple duration effects are applied in sequence for their applicable lengths of time. In this example lets say Chilled got applied then Crippled within 10 seconds of each other and both effects are for 60 seconds in length. Chilled would get applied to you for 66% reduction, Crippled would wait until Chilled had finished then immediately get applied to you for the 50% reduction for another 60 seconds.

The blog post at Guild Wars Insider has a nice graphic to show how this stacking occurs if my explanation is confusing.

I unfortunately don't have any specifics on the timing of specific abilities (such as the Bow's condition removal or each weapon's attack speed), but here's what I can tell you:

• Hammer of Wisdom auto-attacks, knocking back opponents on every third swing. Its active skill can be triggered to perform an on-demand knockdown.
• Sword of Justice auto-attacks, and can be activated to perform an AoE attack.
• Bow of Truth will automatically cure conditions on some sort of regular interval, and can be activated to create an AoE healing rain centered around the bow.
• Shield of the Avenger periodically creates a Shield of Absorption (with the same effects as the Guardian skill of the same name) centered around its location. In this video (@8:30), it appears that the first bubble is cast approximately five seconds after the shield is summoned, but that may have changed since that video was made. You can activate the shield to make it fly out (towards your current target?) and inflict Weakness on nearby enemies.
• All spirit weapons cannot be targeted or damaged by enemies.
• Activating any spirit weapon's "active ability" will destroy that weapon.
• All spirit weapons will despawn after a certain amount of time even if you don't use its active ability.
• You can have up to three spirit weapons active at a single time.