Speaking as a player (and someone who has been reading the obituaries thread) sometimes it really just gets frustrating. After a while of playing both this AP and Shackled City, players sometimes just really get overwhelmed by the fact that the enemy is always so strong, always so prepared, and always a mysterious force that is shrouded in mystery until too late, while the players are open books to be read by the BBEG.
Seriously, after taking a look back at some of the encounters in the AP, you really have to wonder some times how the players are expected to win. Every dungeon is filled with traps and powerful enemies that have the advantage of being rested at the start of every encounter, being on home turf, and fighting as a cohesive unit. And often times, it seems to me that AP creators look on parties levelling as just an excuse to throw more difficult challenges at the party, rather than as a growth experience in both a roleplaying and a rollplaying aspect.
Sometimes, players just get tired of having to slog through every battle, outwit every trap, and put together often scraps of details that are seemingly unrelated to figure out what's going on, just to have to do it all over again next dungeon.
This is not to say that challenges are unnecessary, if there's never a chance for significant loss or death, then the thrill of victory is something that feels hollow and cheap. But at the same time, after a certain point in every adventure path, all kobolds, orcs, goblins, zombies, etc. gain levels in fighter, wizard, cleric, gain turn resistance, gain templates, such that the players, these HEROES who are supposed to be saving the world, never really get to feel powerful. For all of their experience and powerful magic items, everywhere they go, it would seem that evil is levelling just as quickly, and often has homefield advantage.
My advice is as follows. Tone down a dungeon or two. Make it significantly easier. Allow the players to take their power for a tilt around the dungeon as it were. This doesn't have to happen every session, but once in a while, it's nice to have the 10th level or higher cleric who has spent his entire life devoted to his god raise his holy symbol to the sky, cry an abjuration at the vile undead before him and watch them crumble to dust before the might of his god. Sometimes it's nice to see assasins come for the players and find that they've bitten off more than they can chew as the fighter unleashes a full attack, killing two, and cleaving a third. Sometimes it's nice for the wizard to mutter a word and wave his hand and watch his enemies crippled before his arcane power. As it stands in most modules, the players rarely have a chance to show off how powerful they really are since they're always fighting battles where the CR is an "appropriate" level for the challenge, but sometimes it's fun to just be powerful for a while.
Just my extremely long winded two cents.
