By the same merit you would only venture along one path of your choosing to the possible cure, leaving the rest of the map unexplored.
You could choose to believe Lae'zel, and then you would pursue the creche, ignoring anything else, or just try to rescue Halsin and on his advice head straight for the underdark.
That would leave more than half the map unexplored.
From an RP perspective I guess Larian made a story that would heavily discourage any sort of side tracking.
