Hi,
I just wanted to mention that I've noticed some of the cards seem to be missing (not sure how many total)...The 2 I noticed were Woodcutter & Thief from the base game.
Thanks!
Some time ago Donald X. (the game's designer) made a "second edtion" of both the Base Set and Intrigue, where he decided to replace some cards that over time had turned out to be problematic for some reason with other cards. Thief was replaced by Bandit, a card that always gets you a Gold, for example.
You can find detailed info in the wiki at
http://wiki.dominionstrategy.com/index.php/Base_set
http://wiki.dominionstrategy.com/index.php/Intrigue
Dominion Online usually uses the latest version of sets/cards, so the first editon cards not in the second edition are not in the card mix.