@ Fire
If I do Critical Shot now, next level I can do Called Shot (WisMod/encounter ranged attacks can be designated as auto-critical threats). Or, if I probably won't need to worry about creatures being immune to crits, then I can skip Critical Shot entirely, do Weak Spot now and Called Shot next level.
I wouldn't skip it entirely, but it is pretty low priority. For the reasons that CNC stated. Some of them do pick up Fortification or the like incidentally, and at least two opponents do get outright immunity. And that's just of what I've reviewed thus far. But most will not have any real resistance to crit, and certainly not the first few.
Also, the two that are immune are pretty definitely late-game.
To answer your question about Serrenwood from earlier a bit more solidly:
If you guys decide to turn against the gods, then it will help against Hecate. That's the only circumstance AFAIK, and by then, you'd definitely have Force anyway.
Arias: Eager+Warning Shuriken too HighOp?
As CNC said. I don't have a problem with you walking around with something like bronze arrows that are meant to be status-symbols though.
That is pretty greek.
Otherwise, it just helps you in the first round, really, and I don't have a problem with you going first.
First of all, There is no such thing as "Improved Invisibility". There is Invisibility, Greater, and Superior. Improved was renamed Greater in the 3.0 > 3.5 revision.
Second of all, and less semantically, NO.
There is one thing, and one thing only, that grants any kind of invisibility. That is Hades' Cap of Darkness. He lent it to Perseus once, and even then, Pers didn't get to keep it past the time he completed his mission.
As of right now, there's no way Hades is going to part with it. He's using it himself off & on.