reillywareyaDPI should be max, or second to max if the smoothing is noticable on your mousepad.
IIRC, the deathadder is perfect on the default DPI (1800), but sometimes has issues on other DPIs. This might've changed in the 2013 though.
every deathadder model has a different optimal DPI
IIRC the 3.5g is best with maxed out DPI if it's on a cloth pad, and the one that's best at 1800 was one of the models that came before it.
This guy has a 2013 which has a slightly different sensor than any of the other ones (optical light instead of IR light).