Having said that, the concept of Through the Ashes isn't really working. You are playing a group of "non-hero" civilians, which are in fact just regular Pathfinder characters with 15 instead of 25 points to put into abilities, and basically no equipment. You're supposed to avoid combat to a maximum, and combat doesn't give xp, but many combat encounters are still unavoidable, and you'll need the loot they give. Parts of it don't work well in turn-based mode: You need to switch to real-time mode to aggro different groups of enemies to lead them to each other, so they kill each other while you run away. Sometimes you can defeat enemies by dropping something from the environment on top of them, but that usually needs items like ropes and tools, and you don't find that many of these.

In the second chapter, sick NPCs are introduced, and they get sicker and die if you rest. You are supposed to find ways to heal them, but there is only a single cure disease scroll on the whole map, and very few lesser restoration potions. You are playing level 2 characters that don't have many spells, abilities, or healing, and you can't get those powers back through healing. The whole thing feels extremely punishing. And that is not just to me, I watched a streamer with tons of playthrough and guide content on YouTube try to tackle Through the Ashes at highest difficulty, and he was basically reloading every 5 minutes.

I would definitely recommend lowering some difficulty settings for this. The settings where your group members get back up after combat when killed, and get healed of negative conditions on a rest are pretty essential to playing Through the Ashes. It also helps to be aware that there isn't much gear around, and play classes that do well without, for example every class that gets animal companions. I have both a druid and a nature oracle, with two wolves being my frontline tanks. And even with all that, some fights are just hard and tedious. I spent an eternity on the last boss of chapter 2, using multiple grease spells to keep him down, and then rather ineffectively reducing his health with cantrips and ranged weapons to which he was mostly resistant. I also used spoilers like the Survivor Guide, because in the text sequences where you need to assign NPCs to tasks it isn't really obvious who would be suited for which task, so it is either looking that up or trial and error with save scumming. Or letting the survivors die and enjoy the ability to rest as much as you want, in exchange for getting a "bad" ending.

On the positive side Through the Ashes pushes you to use every scroll and every potion you find effectively and get creative to play around the severe limitations of your group. Tactics like kiting help, but aren't usually used in the Pathfinder games. I kited a necromancer in circles, because his animate dead spell only lasts one round per level, which takes a very long time if you do it in turn-based mode. The maps in Through the Ashes have more narrow paths, which works great for spells like grease and AoE effects like alchemist's bombs. Unfortunately the engine used for the Pathfinder games makes blocking a narrow path with a tank much harder than it is in Pillars of Eternity, which I played previously.

Overall, Through the Ashes is a very different experience despite using the same rules and engine as the main game Wrath of the Righteous. But I still think that the follow-up DLC The Lord of Nothing might be a bit more enjoyable, being less punishing.