When replaying Point of No Return, it is absolutely vital to have a plan for dealing with this location (unless you're fine with accepting R2/no resolution) -- it is a mandatory gate for advancing Act 2. Although there are tons of clues available in the other locations, you cannot actually flip Vale of Pnath unless there are specifically no clues on IT, and hitting Shroud 4 without committing or playing cards can leave even dedicated clue-getters subject to the whims of a small number of tokens in the bag unless you can rely on multiple static boosts and/or triggered abilities. For many solo investigators it will be flat-out impossible unless specifically built-around.

(FWIW, in my personal games, I house-rule that Vale of Pnath's veiled ability can be triggered as if there were no clues remaining on it if the investigators have "surveyed the vale" -- with flipping Crag of the Ghouls or Peaks of Thok leading to remembering that the investigators have "surveyed the vale." I think that offers a more varied way for investigators to contribute to advancing the act.)

I'm very late to this, but I wanted to add my 2c.

On a blind playthrough, this card can easily be a full bottleneck. If your clue getting strategy is event based, or commit based, you just can't get past this.

Our blind run was particularly nasty. We had an event based mystic cluever (who was surprisingly good at recycling read the signs 1-2 times every single round) and Nathaniel Cho as our fighter. Without events or committing, neither could get their score above 3, so we were literally digging for 2 tokens while sitting on a place that let us play no events to deal with the mythos deck.

We had to sit on this single location for 6 rounds, ducking in and out of it to play events just to not die to the build up of mythos cards and carefully managing health/sanity. Eventually, we managed to pull a +1 with Agnes (no rite of seeking) while Nathaniel managed to kill an enemy with basic attack actions and trigger Grete Wagner for the other clue.

I'm personally not a massive fan of cards that turn off your deck with no way to counter them. Sometimes the game will turn off committing cards 'or' playing events 'or' assets, but usually not for more than 1 round (or 2 actions to discard the problem). This card is particularly nasty for the fact that it turns off 2 of your potential 3 options and gives you no way to get access to those options again. Really, the way to deal with it is 'play an investigator with 4 or 5 lore'.