When attempting to import (into Lightroom) the TIF files exported by DD, I get “this file appears to be unsupported or damaged”. It was suggested to me that lowering the resolution might work around the problem. In my case, “best resolution” is the whole point of looking at a TIF file.
On a large map it still may be a memory issue.
You can export a smaller area (thus not pushing the memory limit) by cropping the map as described here.
Crop it down and then back up after you export the area of interest.
Is this issue only with Lightroom or are you experiencing it with other software and platforms as well? If the issue is isolated to Lightroom, I suggest reaching out to their support team for assistance.