As far as I know Osttruppen have a permanent x0.5 accuracy modifier for all their weapons, but gain a x3.0 accuracy modifier in cover for just their Kars. This means their Kars have 150% accuracy in cover (about the same dps as Grens squadwise) and their LMG has 50% accuracy in cover.
I tested it a single time some time ago, the LMG performs about the same in and out of cover:
https://www.youtube.com/watch?v=XsOOdDuRlh4
I personally find the LMG lackluster for requiring T4 tech, but the upcoming -2mp reinforce cost could help a bit. Would like to see their LMG have 75% accuracy in cover though.
The patch notes are a bit vague about this, it indicates that weapon should perform 50% out of cover and in cover 75%:
"Cover bonus for slot items from 300% to -25%."
and I could find anything helpful in the editor either other then ostruppen_cover_bonus that seem to apply only to K98. It seem to me that your are probably right and the weapon has the same DPS in and out of cover which is close to your test results.
This is massive nerf from the 50% more DPS damage that they used to do (losing 100% DPS on these weapons). Keep in mind that they had with 2 weapon slots at that time.
The DPS in cover ratio between the Lmg and k98 every 5 units should be:
0.9/1.1/1.4/1.6/1.9/2.2/2.6/2.9
from
2.6/3.3/4.1/4.9/5.7/6.6/7.7/8.6!