Okay, we have now played most of #2 and I am looking at the transition to #3.
I wish the action went back to Trunau. I will probably have to write that bit myself.
Despite my player trying to be circumspect, the game is rapidly losing its challenge. The giants are so vulnerable to magic, and their tactics are so predictable (get close and hit!), that they are sitting ducks. A short list of things they have trouble dealing with: hold person, slow (this single spell effectively ended the boss fight of #2), tanglefoot arrows, invisibility, fly.
The fey sequence in #2 was admittedly a change of pace from this, but I don't see anything like that in upcoming modules, and giants are just not working out well for me as a challenge.
The player proposes forcing all PCs to take a level in an off class, slowing down the spellcasters' progression. I frankly don't think even that will do it. I forsee #3 being fairly easy even with the PCs' current abilities. We'll see how it goes.
We are wrapping up book #2, the boat felt kind of like a railroad, but the Fey / Swamp diversion was more delightful than I expected. One of the players characters is the unknowing father of a changeling...
The fort has also been surprising, it is better designed for multiple approaches than I would have expected. The party used some combo of subterfuge, negotiation and brute force, getting a taste for all of the approaches.
I kind of liked Mary's thought and maybe should've stopped the campaign after part 2. That would feel like a natural stopping point as book 3 is an unnecessary grind.
I do like the idea of Trunau being important again. I've heard there is a giant attack in RotRL, would that be easily adaptable to this AP?
We are now mostly done with #3. The PCs have muffed escaping from the Cathedral with prisoners and are now going to have to fight a whole lot of giants. I believe they will win it, though.
#3 seems severely underpowered. For example, there's an encounter with a CR5 and five CR3 opponents one room before the purported final encounter. The PCs are either 9th or 10th by then. This is not even a speedbump. The enemies have nothing but melee and have trouble hitting the PCs. (My player spared me this fight by Bluffing through.)
The crossbowman with tanglefoot arrows can mop up giants in the open. Tanglefoot is a no-save slowdown preventing the giants from closing effectively. They can't hit at range. Ironically, the AP's deficit of places to shop for magic items set me up for this: he could not find any big magic items to buy, so he bought 60 tanglefoot bolts instead, and really nothing could have been better!
The psychic with confusion can win giant fights single-handed: confusion, vanish, eat popcorn while watching the giants fight. Hold person, slow, and even color spray are also highly effective, as is entangle when outdoors. Note that only one of these is a "person" spell so the defenses against "person" spells are not sufficient. Toppling or dazing metamagics (used with magic missile) are also outrageously strong, so strong the player deliberately removed the feat from his character after one session. He also removed damaging entangle. Giants' reflex saves are almost as bad as their will saves.
My player graciously gave me a party with minimal invisibility and no greater invisibility: the giants are unable to deal with it, except for a small number of ones with animal pets.
On the player's request, I wrote up rules for breaking the morale of the giant camp in #3 based on the ones in #4. I don't really recommend this as it will make #4 feel repetitious. I don't think they are working anyway. The camp is well centralized and the PCs don't have invisibility: their optimal strategy is just to kill the giants piecemeal until they have "accidentally" killed enough leaders to break the camp morale.
The player is talking about abandoning the AP as it's just too easy. He is running only 3 PCs, not terribly optimized, and he's a player who enjoys low-challenge games, but not this low-challenge. I have been giving the giants a bit of help here and there but I didn't sign up to rewrite the whole module....
I hope #4 is better.
Mostly done with #4 now.
It is more interesting than #3 but still not very challenging. What it really needs is a serious response force to react to alarms. Sending two frost giants is utterly inadequate. (My PCs don't move around at night but I think the night response force is even weaker.) I am currently building a force of 8-9 giants and wolves as a second-response team.
So far the PCs have 1 outrage and around 15 sabotage points, meaning that the giant camp will disband soon. They are being fairly careful, which does make the game more interesting. However, they are pushing to do as much as possible each day, which renders many of the giant responses (increasing watchtower staffing, etc.) irrelevant: I think there will only be 2 days of raids in total, and a third day for the Tomb.
The Tomb may be much harder as most of the foes are not giants; but that was true of the temple, and the PCs crushed the forces there even though they pretty much fought them all at once.
My player has made things enormously harder for himself by avoiding many effective spells and pushing to speed-run the whole plateau. Without that I think it would be too easy to be engaging.
The encounter with the dragon is problematic. If she offers information about the Storm Tyrant it tends to push the PCs toward #5 before they are ready. (There is no solid reason they need to finish #4 first, as far as I can tell, other than not leaving a functional giant force behind.) If she doesn't, either she refuses to help, which leaves this whole encounter doing nothing, or she does help the PCs, which will make a rather easy scenario completely trivial.
On my initial read-through #5 was my favorite. I hope it's a more appropriate challenge. Throughout #3 and #4 we get repeated encounters with small numbers of low-CR foes. If you throw CR5 enemies at a level 11 party they will never be able to hit anyone--the only question is how the PCs can minimize resource use. (The bolt ace may run out of bolts eventually, forcing them to waste two teleports to get more!)
I found that it's not so much an army of Giants that is the problem, as the thought of all the various races of the area getting organised.
My character is a resident of Trunau and the idea that it would not be just the standard Orc attacks, but also Giants and Ogres working together, making this a credible enough threat that the PC's need to deal with, before Trunau is wiped out.
The progression has been logical, from the hints found in book one, to travelling Belkzen and encountering the low level monsters, getting more information and working deeper into the Mindspin mountains to reach the boss at the heart of it all.
I've enjoyed it so far, we're just finishing the book 4, book 3 "Forge of the Giant god' was the only book I found too much of grind. The others have had enough changes of pace and scenery to keep me interested.