DAM is damage, damage per individual hit. DPS is damage per second, based on how many times a weapon or technique can hit in 1 second. in a weapon like a sword, the DAM and DPS will be about the same and in the medium-low range, while a hammer has massive DAM but terrible DPS, and a gun has low DAM but high DPS.
Tamn seems optimized for high DAM low DPS, as she lands one or two solid hits and retreats. definitely not brutally efficient, brutlly efficient is going for one single, guaranteed killshot, even if it's messy and causes them to be injured, which requires absolutelt horrible DPS and DAM just as high s DPS is low