D. J. Arneson had an uninterrupted 17-issue tenure on the feature (and then one more issue). This article by Jeff Thompson quotes editor Wallace Green on how, after finishing the first issue's script, Arneson had to hustle with six more pages—they went with an epilogue instead of a second story—when it was decided to publish the issue with no ads.
Arneson is probably best known for graphic novels (as they had yet to be labeled in the Sixties) like The Great Society Comic Book, bylined along with artist Tony Tallarico. With Bill Fraccio's and Tallarico's art at Dell, he wrote the monster superheroes, Frankenstein, Dracula, and Werewolf; I misattributed those books' uncredited scripting some time ago to Don Segall.
To touch very briefly upon writers' styles here, when the scream "Augh" appears for the first time in the series in issue 18, I know that John Warner has come aboard; he's the only one of these four early-70s Gold Key writers to use that particular exclamation (although not in his every issue).
The issue numbers in boldface indicate the ones new to this update.
Dark Shadows Writers
|Mar/69||#1||The Vampire's Prey||D. J. Arneson|
|Aug/69||#2||The Fires of Darkness||Arneson|
|Nov/69||#3||Return for Revenge||Arneson|
|Feb/70||#4||The Man Who Could Not Die||Arneson|
|May/70||#5||The Curse of Collins Isle||Arneson|
|Aug/70||#6||Awake to Evil||Arneson|
|Nov/70||#7||Wings of Fear||Arneson|
|Feb/71||#8||The Vampire Trap||Arneson|
|May/71||#9||Creatures in Torment||Arneson|
|Aug/71||#10||Souls in Bondage||Arneson|
|Nov/71||#11||The Thirteenth Star||Arneson|
|Jun/72||#14||The Mystic Painting||Arneson|
|Aug/72||#15||The Night Children||Arneson|
|Dec/72||#17||The Bride of Barnabas Collins||Arneson|
|Feb/73||#18||Guest in the House||John David Warner|
|Apr/73||#19||Island of Eternal Life||Arneson|
|Jun/73||#20||Quentin the Vampire||Warner|
|Aug/73||#21||The Crimson Carnival||Gerry Boudreau|
|Oct/73||#22||Seed of Evil||Arnold Drake|
|Dec/73||#23||The Cult of the Dasni||Warner|
|Feb/74||#24||On Borrowed Blood||Drake|
|Jun/74||#26||The Witch Dolls||Drake|
|Aug/74||#27||My Blood or Yours||Drake|
|Feb/75||#30||The Weekend Witch Hunters||Drake|
|May/75||#31||The Doom of Helgi Kolnisson||Warner|
|Jun/75||#32||The Secret of the Lighthouse||Warner|
|Aug/75||#33||King of the Wolves||Drake|
|Feb/76||#35||The Missing Manuscript||Warner|