I hope they're considering changes to the Iron Throne sequence. It's the only sequence in this game I didn't have fun with. 6 turns is not enough, and the AI pathfinding in those narrow corridors leads to a lot of frustration.
My main gripe with this sequence is that you cannot trigger the levers with ranged attacks which is suggested in loadingscreen tips.
Apart from that speed potions or better yet, fly will make a huge difference in the outcome. To me it felt like a hard choice moment. Can't rescue them all, must make a sacrifice.
Now the last boss fight..... that thing.... that thing can go straight to the nine hells.
I had no issues with the last boss fight, but I had a Tavern Brawler monk on balanced. After one unfortunate tpk on the run up due to some knock back splash damage, I hasted my monk, dashed, and then jumped all the way to the top in one round. Both boss phases were done in two rounds as the monk action surged and flurried their way through health bars, with the temp member helping clean up with double aoe. The final phase was super underwhelming; it took more time to get in and positioned than to take out it's health. I was really underwhelmed! I'm avoiding monk on my tactician run, and installed a boss difficulty mod to see if I can get things to stand up in the face of my eventual and unavoidable min-maxing.
I played on tactician and it was enough for me to save everyone. It was tough and took some planning, in particular on my wizard, but doable. My last character barely made it up the ladder though. The biggest issue is there is literally no reward for saving everyone.
One key thing I noticed is there are temperature sensors in the hallways. If you heat them (I think, it might be freeze), the two doorways close and lock. This is particularly important to the south, going towards Omeluum. You should send someone through that and, after the two prisoners over there are out, you should then hit the heat sensor with fire (or ice, whichever it is). Omellum can teleport the character out, but the sahuagin spawning that way will be locked out and you can focus on everything else.
You also almost certainly need an arcane gate and some haste or other method of increasing movement.
I managed to do it on tactician, and it was difficult and took a few redos. I don't mind that part, but you're right, the AI pathfinding was a bit frustrating. Some would dash and go nowhere. I ended up having to dimension door one of them, and also used Omeluum's power at least twice to make it work.