As the topic says, the Oculus and Assassin are unlocked in singleplayer for the AI. They are greyed out for the player, but you can select these demigods for the AI. The characters were fully functional in-game, by the way, even if the AI played them really poorly (even by its own standards)
The second issue is a weird sound bug. Any time a voice clip plays, I get a random clip instead of the proper one. For instance, if I order Regulus to move I won't get something usual like "this would be faster with wings". Instead a completely random clip will play, like "the forces of light have slaughtered 30 demigods". While funny at first, it starts getting really annoying really fast.
I haven't gone online (I more or less just play DG with friends these days anyways) to see if these are just singleplayer bugs, but I thought I'd report them anyways.