Prolly already been said but anywho, I dislike the whole chain gang thing. we are not criminals!! We are okay some of us may or may not be, but we're not imprisoned the tadpool is.
Keep the whole ability to move characters on the lower left screen, first one is the leader, second is next, third is after that, fourth is the last person. There a simple formation.
Chain gang Moridains beard add a button or ability to right click on a portrait and an option to remove from group. Then when you want to readd them just right click, add to group option.
Formations are not really needed imo, but they will add more to the game then they will detract. You can keep it simple square, line, triangle, or diamond (cause you know there forever). Simple easy to use well maybe not the square. that may require something else like a formation screen to properly position. Though in truth any of them may.
I do like how smart the enemies are avoiding puddles for the most part, attacking my wizard first, trying to put my fighter/cleric to sleep round. It is far and above better then many or perhaps all other games out there. Now if we can only get my group to stop running into random vines, fires and other things. Some of that is on me but still, seriously Fang Elf would you stop!!