Frankly I'm also not a big fan of a "chain", neither in D:OS2 nor here. Larian has a ton of great ideas, but this, IMO, is one case they are probably wrong. I would prefer some smarter system that allows to select one part member by single click and direct only him, then maybe reset this selection some way, even if by just good ol' box selection of all portraits.
There also needs to be some tolerance to small movement by a leading character. Right now even small movement by selected character causes your whole party to often run around regrouping and what not. Relax guys, I just moved 2 centimeters towards a vendor or some NPC, no need to raise such a fuss.
Switching to another character to cast a buff makes them all go wild too there, like here in this example in this vid: