I have 2 linos both with QA +3 and i im 99% sure i used dusktip (since i went with what bg wiki said).
I was talking about DA, not QA.
DA is in the Leaf slot, shares the slot with STP (and other stuff).
QA is indeed in the Dusk slot instead, just like you said.
In general for augment slots that don't have many possible values (like the DA or QA slots, they both have only 3 possible values: +1, +2, +3) then using +1 stones is cheap and very efficient.
For augments that have a huge range of values (like Acc, Att etc, ranging from +1 to +20 and the likes) then in the long run it's probably more efficient to use +2 stones if you really want to reduce the range of possible value outcomes?