I think Venli is group 3. Brandon itself says that group 3 appears and have roles in group one.(but they have no povs)
And group 3 also appears as the same time as the flashbacks appears. So its the perfect time to introduce Venli and her flashbacks.
So i say, group 3 is Venli and Moash
Group1 Kaladin, Adolin, Renarin Lirin(few viewpoints) and the 5th one maybe someone of the bridge4
Group2 Shallan, Jasnah
Group3 Venli ,Moash
Not appear: Dalinar(Sanderson previously said he will had a small role in this book,so he doesnt need povs), Szeth(idk what his role would be in this book, if he doesnt go to Shinnovar until 5th book, i think with only interludes about his training is enought) ,Lift
This is my guesses