So basically if we want this pool to succeed we're going to need more people, because while it won't make it 100% that we will find a winning hash faster, we would at least have a higher probability of hitting one faster.

Correct. Your chances of hitting the lottery is the exact same, no matter what combination of numbers you play. Play more numbers, you have a better chance.

So with more people guessing the hash, the better chance you have of finding it. It could happen on the first try, or the billionth try... really no way to know... AND remember you're competing with everyone else, so if you don't find it before someone else does, the whole thing resets and everyone starts looking for a new hash.

So it's all in the luck of the draw.