6 is too many for a turn based game like this IMO. Some of the longer fights in act 1 already drag out a bit long and thats with 4 chars to control. I’d bet they play-tested 6 earlier in development and decided yeah this is too slow.
I dont understand this premise ... More ppl means you get to your turn more often ... meaning your party do more damage .... meaning combat is shorter on the contrary. O_o
I mean you still control single character at the time that dont change.
It also means changing every single fight by either increasing the number of enemies you fight or increasing their HP pools/number of abilities to keep the same difficulty. So yes your party does more damage but the enemies would as well do more as well as soak more. Net effect is longer combats with more turns total as i said. It sounds like you have never developed/balanced games so ill let it slide
Not to mention this late in development if they have been balancing every encounter for a party of 4 then suddenly changing to six is not going to happen.