The devs announced that they are going to create encounters where the parties will be far away from each to avoid one-sided alpha strikes but I do not think that would be always possible and the gameplay implies that you can sneak to place your party near the enemies or divide the party in exploration mode to lure the enemies in a Mutant Zero style, so I think they will have to do something to make the encounters balanced.
That said, there are games with group initiative that makes the combat challenging even if you go first, like the Age of wonders: planetfall, x-com games, etc.
