Modpack version
1.7.5, with optifine

Issue
putting in tiny piles of cobalt/ardite dust should result in them compacting into cobalt/ardite ore dust, all other tiny piles of ore dust(from jaopca, the ic2 ones behave completely differently) properly compact in storage drawers.
this is a twofold problem, the reason why cobalt/ardite dust don't compact properly is that a recipe for small piles(4 for a dust) and tiny piles(9 for a dust) are both craftable depending on where you place the dust in the crafting recipe, all other jaopca dusts, while having both crafting recipes, the tiny piles take precedence over small piles recipe, and the small dust is uncraftable.
you can fix this by setting custom rules for compacting drawers for the jaopca dusts(as far as I can tell, nothing uses the small piles of ore dust) to correctly convert them, and allow crafting of the small piles of ore dust, OR, you can just straight up remove the small piles of ore dust crafting recipes which would also fix it.

EDIT: if you chose to add the compacting rules, they would be these:

exnihilocreatio:item_ore_cobalt:2, jaopca:item_dusttinycobalt, 9
exnihilocreatio:item_ore_ardite:2, jaopca:item_dusttinyardite, 9

also applies to thorium and boron, here are the compacting rules for those:
EDIT: and magnesium

nuclearcraft:dust:3, jaopca:item_dusttinythorium, 9
nuclearcraft:dust:5, jaopca:item_dusttinyboron, 9
nuclearcraft:dust:7, jaopca:item_dusttinymagnesium, 9

Thanks for the report, and the solution :D

It doesn't seem to work for any Small or Tiny pile, at all. I've tried about 20 different ones now, none of them can be compacted in Compacting Drawers.

How are you compacting the tiny/small dusts with Compacting Drawers?

Osmium, Nickel, Platinum, Aluminum all properly compact,
sidepoint: just to be clear, small piles and tiny piles working at the same time is an impossibility for 1.12 storage drawers, but since nothing uses small piles, they don't need to be the ones that work with compacting drawers.
The ones that properly compact, you can see both the tiny(9x) and small(4x) crafting recipes are identical, with the tiny recipe showing up first.

This should be fixed by the next update :)

Would you mind checking if the issue still exists in 1.77? :)
Uploading it now.

Would you mind checking if the issue still exists in 1.77? :)
Uploading it now.

I'll test it as soon as I can.