Wouldn't be surprised if the success Escape of Duckov has made other developers think the same. Make it a bit more serious add co-op. Formula works.
Reason many are still vocal about the PvE part of Arc is that the initial trailers/information about the game was that it was designed as a F2P PvE co-op game against the Arcs, but they changed it mid development because they concluded that their studio wasn't big enough to sustain it. Which I understand and think it was the right choice, would need much more content to make it like Destiny or The Division. Especially in the style they made the game. Smaller studios probably would have a much easier time building on the top down style of Duckov to make a PvE game