In the dreamland asylum packs, the dreamland fanatic is just the only one usable for Cthuhlu. Maybe In an unmarked grave, but it could do more damage to you than your opponent.
Terror from the tide, nocturnal scavenger, called by azatoth, are good cards, but they aren't in the dreamland pack. Furthermore, Chtulhu lacks good 3 cost or less caracters. The cthulhu mono faction deck is not a good idea if you want my opinion. Well, all mono faction decks are very weak.
But the syndicate, and dreamlands syndicate is the worst in mono faction. Panic can't save you all the time and the mecanisms developped in the dreamlands packs aren't synchronised with the syndicate mechanisms of the core set. Worst of all, the dreamlands syndicate mechanisms are useless. the opponent draws cards all the time thanks to you and?