Those tactics look fine to me.
I'll take a crack at some flavor text, based on the Ash:
Dust quasi-elementals are embodiments of entropy from the Quasi-Elemental Plane of Dust, which is formed from the junction of the Negative Energy Plane and the Elemental Plane of Earth. While they might seem evil, dust quasi-elementals are not much different than a tornado or mudslide in motivation. Destruction nourishes them, and great devastation can spawn more of this kind.
Leaderless mobs of dust quasi-elementals roam the Quasi-Elemental Plane of Dust, disintegrating whatever they find. They make no special effort to leave the Quasi-Elemental Plane, but they make no effort to return if they find themselves elsewhere, either, content to wreak havoc whereever they are.
There's nothing about them being spawned from destruction in the original monster, so I think we should cut that bit out.
For the description, the 2E version has "looks like a billowing cloud of dust, with tiny, eyelike pockets of swirling particles" and 1E "billowing clouds of dust, dominated by brighter motes which are collected into the “eyes” of the creature".
The 2E version also says "It revels in the obliteration of solid objects, especially the pulverization of worked or crafted materials" and the 1E "They are rarely found in the Prime Material plane, and then only in desertlike regions where the winds have pulverized most of the earth to sand".
In addition, Dust Quasis are prone to attack those that provoke them - in 2E "if crossed, a dust quasielemental stops at nothing to slay the berk who did it harm", and in 1E "unlike other quasi-elementals and elementals, these creatures attempt to seek out the ones who have enslaved them and slay them".
I think we should work those details into the description.
How's this...
A billowing cloud of dust, with eyelike hollows that swirl with glittering motes.
Dust quasi-elementals inhabit the Quasi-Elemental Plane of Dust, which is formed from the junction of the Negative Energy Plane and the Elemental Plane of Earth. Dust quasi-elementals are living embodiments of destruction, who revel in the pulverization of solid objects, especially manufactured items. These quasi-elementals are dangerous and vengeful. They will try to destroy anyone that crosses them, but are no more evil than a tornado or mudslide.
On their native plane, dust quasi-elementals wander around without any organization or plan beyond disintegrating anything they come across. They occassionally cluster into leaderless mobs and wreak great destruction. Dust quasi-elementals are content to destroy matter whereever they happen to be. They have no interest in leaving their native plane, but if forced to do so they are just as uninterested in returning. Spellcasters tend to avoid summoning dust quasi-elementals, because the vengeful creatures attempt to seek out and pulverize anyone who attempts to capture or enslave them.
A dust quasi-elemental has the same height and weight as a X elemental of the same size.
Sorry I've been so slow posting. It's been pretty crazy this week both personally and at work. Since I'm hosting a conference in a week and a half, I'm not sure work will be much better for a while, either.
Well one can hope!
