Joe --
At Chickamauga the 6th Georgia Cavalry served with Davidson's Brigade, not Armstrong's Brigade.
General Pegram's report for his division reads, "My loss in this fight was about 50 killed and wounded, numbering some of my most valuable young officers." Col. Scott's report of losses lists ten officers killed and mortally wounded for his brigade. Evidently Davidson failed to submit a report for the Battle of Chickamauga.
If all the above is correct, my math suggests that six killed and mortally wounded for only one of Pegram's regiments would be disproportionately high, not low.
Is that what you really meant to write?