I like the variant as in the Pathfinder bestiary. Nice.
Let's do HD the same as regular skeleton template, remove DR, reduce natural armor and claw damage as suggested. Agreed to that. I can also see increasing the aura/trail and death throes areas by size or HD.
Well I'd cut the Hit Dice to roughly half or three-quarters the original, but if no one else fancies that additional complexity we can just use the regular HD.
I'd rather key the aura/trail dimensions to size and leave the HD to just affect the DC. Here's a rough draft:
Aura of Dust (Ex): A dust skeleton constantly emits a cloud of irritating dust, which spreads out to a distance equal to twice its Space (e.g. a Small or Medium sized dust skeleton has a 10 foot radius Aura of Dust). All living creatures which enter this cloud of dust must make a DC
X (
Fort? Reflex?) save or be
dazzled for Y rounds. The save DC is (
Strength?)-based.
Death Throes (Ex): If a dust skeleton is slain its body explodes into a burst of toxic dust, affecting all living creatures within a radius equal to twice the skeleton's Space (e.g. a Small of Medium sized dust skeleton's Death Throes affects a 10 foot radius burst). Creatures within the area must make a DC
X Fort save or
be nauseated for Y rounds and then sickened for Z rounds, creatures that make their save are
sickened for A rounds and then dazzled for B rounds. The save DC is (
Strength?)-based.
Trail of Dust (Ex): A dust skeleton leaves a trail of dust wherever it goes. Any creature attempting to track a dust skeleton by sight receive a +X circumstance bonus on their Survival checks to track the skeleton. This dust trail is a strong irritant, so creatures attempting to track its trail by scent are affected as if they were exposed to the skeleton's Aura of Dust (see above).
The bits in red are where I think it needs work. If we make it Strength-based it would have a rather low DC, so it may require a racial bonus on Death Throes.
I'm not sure about the effects of the Death Throes. Nauseated for 2d6 rounds on a failed save or just 1 round on a successful save would be closer to the original description, but I don't like the 1 round of nausea even on a failed save. Maybe nauseated 1d6 rounds and sickened 1d6 rounds on a failed save, sickened 1d3 round on a successful save? That's nasty, but not automatically incapacitating.