I can confirm that it does work pretty well as a pure co-op.
Our group plays where we have to defeat the end boss and have a certain amount of points to win.
We have been playing at 20 points per player so in a four player game it would be 80 points total as a group not each player has to have 20 points or more to win.
We are probably going to increase it to 25 per player next time that we play because we have won every time but it has been VERY close in the points area.
Our group REALLY enjoys the game as a pure co-op.
I really hope they release expansion(s) for it as I know that I will buy them. I would love more of everything that the game already has.
Here is hoping that there is expansion(s)!!
Like Robert mentioned, you can! Just don't count the points for a single person to determine a True Guardian. I do like Robert's suggestion to add up the whole groups points to determine if the party was successful. I may put that into the rules for the reprint / expansion!
I have the expansion designed and being tested right now, I just need to sell more units of The Guardians: Explore to fund the art creation for the next title.