They can set up a new camp and introduce new companions in Act 2. Someone not suffering from the 'condition' of the others would be interesting. They have all the time in the multiverse while the others have more urgent needs. The most important thing seems to be that there is a reason for reducing party size. The fact that the whole Mindflayer problem creates a strong shared goal makes a split hard to explain.
I sometimes use thought experiments. I don't necessarily believe in every idea I post for discussion on this forum
