I believe that dust users who focus on a single dust type would be better off using dust infusions, dust based mechanisms, or small crystals. ___________________________________________________________________________
It's true that increasing the surface area of a reactant speeds up the reaction. In this case, the faster it is, the more volatile and "powerful" it is.
It's like lifting a box vs pushing it up a ramp- there are scenarios where lifting a box is simply better than pushing it up a ramp. It would be foolish to say that ramps are not effective, as they provide a degree of safety to avoid injury.
However, explosiveness doesn't make powdered dust viable- if that were so, then Nora's grenades, which are way more explosive, would be way better than Weiss's spells. The strength of dust comes from its versatility, not its raw power.
In smash, Little Mac has enough damage and speed to out DPS a large majority of the cast. Some people would argue that this makes him a top tier, but his lack of aerial mobility and range make him bottom tier.
Powdered dust is simply not as combat viable as small dust crystals, which keep most of the advantages of powdered dust without its weaknesses.
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From what I can tell, here are the pros/cons of powdered dust:
Pros:
Can be used in dust infusions
Provide speed when needed
Is easier to store
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Cons:
Has to be stored in specific compartments or infused to avoid accidents
Dispensing dust like Weiss makes it extremely difficult to cast dust spells while dodging (You dodge, but the powdered dust is still trailing behind you).
Can be detonated by a sneeze (Sneezes travel at 100 mph. A bullet can fire over 1500 mph)
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It's clear to me that powdered dust (dispensed using the gun and canister method) just has too many disadvantages to compete with other options
The reason why: any dust "spell" cast by the user would require the user to be standing in the same general location/ facing the same direction. Powdered dust dispensed using the gun/canister method would not follow the user when they are running. Unless they are dispensing a small amount of dust each second (which would be essentially the same as using a dust crystal), the gun and canister method would produce weaker effects in a potentially undesirable direction.
Even you have to stay still for only a fraction of a second, it seems unlikely to me that any well-renowned huntsman besides a dedicated dust mage would do so.
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Proof:
Most of the martially focused dust users (Ex: Adam, Octavia, Sienna) do not dispense powdered dust in the way that Weiss does. They rely more on their agility to dodge attacks, unlike post Volume 3 Weiss and Leonardo.
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The point is that powdered dust may be too easily dispersed to be used effectively without infusing it into an object.
Weiss and Leonardo are exceptions, being frequent users of multiple dust types. (Weiss favors ice, but also uses hard-light and fire frequently).