I also have the Developer's Cut version from GOG, but have not played through the PC version yet, so couldn't check the achievements there. I don't know of any achievement lists specifically updated / confirmed for D2:DC (the wiki also lacks the Dragon Knight achievement for DKS, so it may have just been copied from the Xbox list, which incorrectly has 'I trained a pet' instead).
I know Ygerna calls you a pet, but training a pet is her achievement, not yours, so unless the name of that achievement is in quotes, it doesn't really fit the description, IMNSHO.
For example I do not seem to have "Adrift" as well.
Did you find the raft outside on Sentinel Island (hung up on some rocks, away from the island, in the direction of the fjords) and read the diary there (after you took over the battle tower)?
