To be clear, I didn't state that having sufficient blockers means you are ahead on board - I qualified my statement about having sufficient blockers saying it probably, but not absolutely, means you are ahead on board. The general point I was making is identical to what you said afterwards. I agree with you that this card probably shouldn't be characterized as a "win more" card in that sense.
Ultimately, the card is very polar - if the board state is such that you can protect this for even one turn there is a strong likelihood you win that game, if you lose the monarch though this card gets much worse for you. As someone who advocates for the role of Baneslayer type creatures and the "do they have removal or not" tensions they create, I suppose I should like this card with its similar "answer it (via removal or stealing the monarch) or lose" implications.
Not sure how my post which literally opens with discussion of the monarch mechanic is disregarding monarch?
My point was that this card is a bit of a win-more card. If you have sufficient blockers (which probably means you are already ahead on board) before you resolve this on turn 3-4, you will probably win having gotten 2 cards and a 4/4 angel for 2WW by the end of your next turn (in addition to your other spells) with further value to come for no additional investment. If you draw this later when behind on board or can't drop this on turn 3-4 without losing monarch, the spirit tokens don't make up for giving your opponent additional cards and they can't attack until two turns later meaning your opponent could net multiple cards before you reclaim monarch. In sum, if you're ahead on board this will often close out the game. If you're behind on board this isn't particularly good. I may test this yet, but as stated I have reservations.
I agree that Palace Jailer is extremely good. If I can get even a couple other cubeable monarch cards from this set or a future set, Jailer will go in along with those cards. I want at least a little interaction with Monarch though (besides stealing it via combat damage), I don't want Jailer to be the only cubeable card that grants this ability.
I wasn't too keen on the Monarch mechanic when Palace Jailer and arguably Custodi Lich were the only cubeable options with the effect. Did not seem worth adding in this minigame over a single card. Now we've got a few additional options that might make it worth the while.
I have some reservations about this card. This doesn't create any bodies until your next upkeep which leaves you pretty vulnerable the turn after you cast it and your first spirit token won't be able to attack to reclaim monarch until turn 6. If you have the board-state to protect yourself and this starts creating Angels, it becomes unbeatable. It's very much a great when you're ahead and subpar when behind kind of card. If anything, I tend to favor tide-turning cards over cards that reward already being ahead.