As the player who has perhaps spent the most time mastering the terrain tool and building some truly unassailable defenses I think I have a unique perspective on this issue. The terrain tool, even in its current implementation, is capable of creating completely unbreakable defenses, but it requires hundreds of hours of experience and experimenting to be able actually execute in a timely fashion. It is thus understandable that many players who have less time to learn want the terrain tool to be buffed so they can also build such fortresses. However, if terraforming was easier while retaining its current power it would absolutely break the balance of the game.
I think it is really fun and satisfying to build impressive terraformed fortresses, and that many players would have a more enjoyable game experience if it were made more possible for them. And so I’ve thought a lot about ways that terrain’s defense potential could be toned down a bit so that it doesn’t trivialize the game. Ngl, I don’t have any good suggestions though. If raiders could climb up and down cliffs it would still be effective to slow them down but make it much harder to funnel them into a single chokepoint, but given the discussions around water and pathfinding I suspect the technical implementation of this would be too much to realistically do. If some raiders could fly it would reduce the effectiveness, but flight doesn’t fit the setting. Etc.
So the point of this post is really just that I wish it were possible to make terraforming a bit easier without making combat trivial, but I can’t think of a realistic way to actually achieve that. It is a very hard thing to balance, but hopefully the devs can think of something though, because I really think it would give the game a cool factor that sets it apart. I think in terms of balance, on normal difficulty it should be fine to defend without thinking much about terrain, but success on the hardest difficulty should require taking it into consideration.
I made this post after loading up a past save to see how it handled the new raiders, and without any changes it slaughtered them all including catapults without any issues, so it is still (too?) strong. One immediate change that would help the raiders is to make catapults target anything within range, rather than targeting the first building they can path too. Currently they will happily roll into range of a tower on a cliff and not return fire until they are shot, making them too easy to counter.