apply viewport scale factor there...
That is a very limited-scope solution, imo, which may work for some instances, but leaves one with an inflexible situation that requires much manual work.
1- I would suggest setting DIMASSOC to 2.
2- Leave the dimension-style settings as you have them.
DIMASSOC is a system variable that is set on a per-drawing basis. It is not set across-the-board for any drawing you open. It can be set to 1 in one drawing, 0 in another, 2 in another. So the drawing you pasted the model into, it may have been set right. The drawing you /had/ it in originally may have had dimassoc set to 0.
If you have DIMASSOC set to 1 or 2, it will read the scale of the VIEWPORT and the dimension will scale appropriately (assuming you snap tot he objects in model space through the viewport, when you're placing dims in paperspace)
If you have DIMASSOC set to 0, the scale of the dimension will stick stubbornly to the scale set in the dimension style, which you have set to 1.000.
DIMASSOC=2 means never having to set your dimension scale - only your viewport scale. This is a solution that works perfectly for any drawing, regardless of the number of sheets or viewports. If you have a viewport at 1:4, and have a 1:1 detail inset, DIMASSOC=2 means you can keep creating dimensions on any viewport and they'll read correctly.
DIMASSOC=0 means you have to manually chance the scale of every dimension or have a separate dimension style for each 'scale' of dimension, and apply the scale to the appropriate dimensions.
DIMASSOC=0 = wasting time, imo.
DIMASSOC=2 = leaving your time to worry about more important things.