Bit of a minor point this, but why doesn't the Monster deck have its own designated placement spot along the side of the board like all the other decks? Seems a bit of a design flaw, or have I missed something?

Similar to the Rune deck not having a spot. I suspect it's a design limitation, not a design flaw.

Yes, I guess so. I'm not so bothered about the rune deck, as these cards aren't drawn regularly during the game. None of this really matters of course but it seems odd when the board is designed with specially marked spaces for decks.