The way I remember it, in Original Sin 2 the turns switch between the participating parties regardless of the initiative differences between the various combatants. The individual order is based on initiative which is increased by levelling WITS and a small amount of temporary buffs.
For example if you have a party of
Character_1: 12 initiative
Character_2: 13 initiative
Character_3: 10 initiative
Character_4: 14 initiative
And fight the following enemies
Enemy_1: 15 initiative
Enemy_2: 21 initiative
Enemy_3: 22 initiative
Enemy_4: 10 initiative
The order is
Enemy_3 (22 ini)
Character_4 (14 ini)
Enemy_2 (21 ini)
Character_2 (13 ini)
Enemy_1 (15 ini)
and so on...
It's honestly exceptionally stupid and one of the design decisions that, in my opinion, gets overlooked way too frequently whenever people want to criticise the game.
