Yes, it's a complete mess. Managing the party in itself is a frustrating mini-game.
If the the "party" UI and functions will remain unchanged, then we need at least a keyboard map to unlink all and another to party them up again. Also each character needs a hardcoded F1 to F4 link, so F1 always selects the same character and they never switch places. Clicking with mouse doesn't select them, like needs clicked 2 or 3 times until reacts.
This stuff should have been seen during early Alpha; it's very bad coding and party management "solution" for a game that constantly needs to select each character, one by one, all the time.
IIRC party movement was one of the last aspects they added to the game. When they were doing demo videos each individual character needed to be moved individually. I guess the devs were doing playtesting in multiplayer only or something.