Paul: Yet a third might be that we can't aggregate the pain of dust harassment across people, so that there's some amount of single-person dust harassment that will be worse than some amount of torture, but if we spread that out, it's not.

My induction argument covers that. As long as, all else equal, you believe:

• A googolplex people tortured for time x is worse than one person tortured for time x+0.00001%.

• A googolplex people dust specked x times during their lifetime without further ill effect is worse than one person dust specked for x*2 times during their lifetime without further ill effect.

• A googolplex people being dust speckled every second of their life without further ill effect is worse than one person being horribly tortured for the shortest period experiencable.

• If a is worse than b and b is worse than c then a is worse than c.
  

...you can show that all else equal, to reduce suffering you pick TORTURE. As far as I can see anyway, I've been wrong before. Again, I acknowledge that it depends on how much you care about reducing suffering compared to other concerns, such as an arbitrary cut-off point, abhoration to using maths to answer such questions, or sacred values, which certainly can have utility by keeping worse irrationalities in check.