Does anyone know if it's possible to cross the mists without "plot armor" (not literal armor) in act 2? When I tried exploring it early I could still access the area, although I got horribly slaughtered as reward for my curiosity. When I crossed it later I did not notice any particular barriers... Anyone tried making a run for it yet?

I haven't, but when you first crossed it at the very beginning of the Act after the summit between the two sides, I did notice if you left the protective bubble, your Vitality would constantly drop all on its own.

So....my guess is you can't without some protection. Give it a shot and let us know! ;)

I think you might also not be able to get to the other side because you won't have the talisman/owl guiding you (so no matter how far you run you'll never reach the blue misty part that takes you back to the real world).

Nope. I don't think it is the armor as much as a pendant (if you are on the path that I think you are). And I think you can only pass safely when the main quest requires you to cross the mist. I think I tried crossing it when there is no such requirement by main quest and got one-hit even though I have the talisman.

You should die in 1-2 hits if you try to cross it without plot armor. And even then, I'm not sure you can reach the other side.