Cosmic Revelation turns a Play Action and a card in your hand into one Draw or Play action for each player at your table. Assuming you value every card in your hand as being worth one action, Cosmic Revelation's value scales proportional to the player count:

• In One-Player: Cosmic Revelation is action negative.
• In Two-Player: Cosmic Revelation is action neutral.
• In Three-Player: Cosmic Revelation effectively provides a bonus action.
• In Four Player: Cosmic Revelation effectively provides two bonus actions.

Personally, I tend to play 3-Player or 4-Player campaigns, so I expect Cosmic Revelation to become a staple at my table. Even if no one at the table needs (or can't afford) to play cards from their hand, free card draw is almost always helpful.

definitely a card designed with Agatha Crane's ability in mind

playable in either class flavor and desperately wants to played fast

certainly higher player counts encouraged, but even solo its perfectly fine to play for free off her trigger after committing it

It has been mentioned in previous reviews ans comment that:

• it gives additional actions at 3 / 4 players,
• it allows investigator A to play a card during investigator B's turn,
• it allows this investigator A to avoid an attack of opportunity,
• with Farsight you can give it Fast, to get an additional action bonus and potentially to avoid an other AoO.

With the Spell trait, you can also attach it to Dayana Esperence in a support deck.