My PCs took out Gogmurt but not before a warning was sent to Thisteltop and the alarm was raised.
The party was severely messed up. Most spells were used up and the barbarian was near death (The cougar really roughed him up)
So the party decides to sleep in the tunnels, keeping an eye on Thistletop to make sure noone comes from that direction.
The way I played it so far is that the goblins in Thistletop shore up. Expecting an attack,they prepare and hunker down.
But how long would they do so? They're goblins so their attention span isn't the best. How long would they wait before they got bored and their security became lax again?
The same thing happened to my party and I had the goblins send out scouts (2 commandos) at night to see if the party was still in the tunnels. Once a fight started, a few more goblins and a couple goblin dogs also came into the fight.
The party was already hurt so had to fight and withdraw, and camp further away.
I prefer my enemies to respond that way, to keep my players on their toes.
If the thickets have been cleaned out, resting there is not a horrible idea. At least if the party is smart enough to put a sharp guard on the bridge.
The goblins have only one way to get out. So if the party is awake they should have a good chance to see any goblins trying to sneak across. A really clever party would rig the bridge so they can drop it on the mainland side but still pull it back up after surprising anyone trying to cross it.
The goblins have no real way to get at the pc's except via the bridge. But that's not true for everyone in Thistletop - Yeth Hounds I'm looking at you. But that would imply a much greater degree of cohesion and effective response from Nualia's organization (using that word loosely) than is established in the AP.
You could also have the goblins be a bit smarter, perhaps the sneak to the cliff's edge and using bird calls or other vocal signals try to confirm there are survivors on the mainland. If they don't hear any response or the right response, they retreat and try to shore up their defenses. Again this makes them more effective tactically than might be assumed with goblins...
As a result they ended up fighting a larger group at the front door while being shot at from both towers
I used the same strategy. but since my dice hated me (as usual), the goblins started to strangle themselves with bowstrings and shot themselves instead of shooting at the group. it was a very goblin-y thing to do, so I just added extra goblin guards behind the doors and didn't mind