1) Stock up on poison moss. Damn near everything in the DLC will inflict poison biuldup.
2) A decent ranged attack (either bows or the spellsnipe trick) are required to access most of the secrets, as well as helpful for dealing with the archers that are all over the place.
Other notable things;
1) The Puzzling Stone Sword, which combines the light attacks of a shotsword and the heavy attacks of a whip. Also has dex scaling out the wahzoo.
2) One area accessed about halfway through is the new best place for farming dragon bones, provided you can reliably kill the things that drop them.
3) Flynns Ring. Basically acts as another RoB+2 if you have your max equip load at 60 or lower.
4) The Drakeblood Greatsword, probably the new best dex greatsword.