Ad.1) Their telepathy has only 100 ft. range, but if they are in that range, why not coordinate? It's a unique challange for players. Let them roll knowledge check to realise that.
Ad.2) Just give them another knowledge check, btw any respecting wizard already has wand of Dimensional Anchor on their person ;p If enemy escapes few times players feel that defeating them is something they really deserve through their hard work.
Ad.3) If players choose to be part of the Pathfinder expedition give them Wayfinders. Clear spindle Ioun stone when put in a Wayfinder generates resonance effect giving Protection From Evil effect on a holder (only vs suggestion/charm/dominate line of spells casts by the evil enemies) - problem solved!
Prot/Evil 10'r stops telepathic communication and control across its boundaries. Combine with Widen and you can make a Telepathic 'bubble' to contain alarms with some effort.
Sadly, no Proof against Teleportation, it's a 3.5 spell. Yes, definitely invest in Dimensional Anchor, which is way too high a level for what it does. There's also a sword effect which stops teleportation, I think.
There's also the whole kill them before they can teleport away thing, and dispels to remove contingencies.
==Aelryinth
1. Keep it in the game, it is a unique challenge and part of the challenge rating for the monsters. If you drop it you also rob your players of the unique challenge of defeating such a creature. With out it they become "just" another monster. Have faith that they will adapt and over come.
2. The first time it happens they will realize the issue and come to terms with the needed measures. Keep in mind the DC for Casting defensively is no joke, just because its on the list, doesn't mean they will get the spell off.
If your players let them move into a position that he can simply cast and bail, well, they learned a valuable lesson. One that maybe they didn't learn earlier, letting a caster work unimpeded is asking for pain.
3. On this I think some hints that Iron WIll and Improved Iron will are good investments is needed. Still, if they create characters with low will saves, hit them. They will learn to deal with it or suffer. The first time the fighter or Barbarian turns on them they will learn to keep an ace in the hole for emergencies.
If you can fool them with the same trick on 1,2,and 3 more than once, might want to have a talk and remind them of options. Your fun is executing the tricks, because you will likely only get to hit them like this once! So enjoy!
Yeah. The only real peril in this AP is from other party members.
IOUN stone helps , but confusion is still an issue. Gets tad dull when it happens too much. In mod 5 at this time.