Thick Skull seems a bit dubious

[Coaxl]

Thick Skull seems like a nice little feat and I took it for my character, but I quickly found that it sometimes works in a very dubious fashion. It is all well and good that it leaves me only Dazed when I'd be otherwise stunned (which is useful, for example, against crossbow enemies using a few Shock Bolts or psions using a few electric attacks at the start of the battle), but the problem is, there is no "Second Wind" anymore. This, in turn, means that enemies that can stun me every turn with their attacks (Coil Spiders! As well as anyone else using strong electric attacks on a regular basis) can also daze me every turn. This actually seems to be a bit of a downgrade in a way - without Thick Skull, I was immune to stunning effects for the two turns of Second Wind and didn't get dazed either, while now I get -15 AP every turn. We could also look at it this way: stunning removes 50 AP (if you have not boosted your APs) and the ability to dodge and act, but then you are immune for two turns. Now, over the course of three turns, getting constantly Dazed means that I lose 3*15=45 AP. More specifically, using a crossbow with an AP cost of 21, and assuming no AP boosts, I lose two normal attacks when I get stunned, but I lose one normal attack each turn with the "constantly dazed" option, which actually leads to repeated "Dazed" arguably being worse than being Stunned and no Thick Skull in certain situations, at least for my character.

My suggestion is simple: have a "Second Wind"-type of effect apply to "Dazed" as well, for characters with Thick Skull. (I.e. you are immune to being Dazed as well for two turns.) That'd make the feat a clearly superior option in all cases to fighting without it and make the feat more useful in general.

[Hazard]

Out of curiosity, what kind of character are you running with? I'm not an expert by any means, but Constitution 10 and crossbows aren't the first things that go together in my mind. That might just be me, though.

In any case, I agree with you that it's not particularly good for your attack power if you stay dazed for several turns. On the other hand, while dazed you're not a sitting duck with zero evade/dodge (assuming you have any) like you would be while stunned, which is pretty huge, and you can do quite a few things with 35 AP, depending on your skills. For example, heavy armor riflemen don't really care whether they have 35 or 50 AP: with a fast 11 AP assault rifle they can still burst once (or twice with Commando) per turn, which is often enough to put an end to constant stuns/dazes.

[Greep]

Thick skull matters more if you adrenaline every tough battle, which I personally do

Then it's a matter of losing a precious turn of adrenaline boost or suffering a mere -15 AP.  Also it's pretty crucial for evasion builds.

[Coaxl]

I'm doing a build that focuses on crossbow and stealth, with high Constitution and Perception (both 10 at the moment, somewhere between level 16 and 20 right now) and good Agility and Intelligence (I think they're at 7, or Agi may be at 8, I'm not sure). Basically, it's my first character, and the idea I had before starting the game was: light, evasive and stealthy, but with a lot of HP just to be safe.

[blamzooie]

Thick Skull is a 10/10 feat when it comes to endgame. You get stunned so often by all kinds of bullshit. Losing every other turn is not really a fun way to play the game