Regarding the player knowledge factor (that is, how to deal with players knowing what the other PCs are up to), in my experience players take a fiendish delight in roleplaying (correctly) that they have no idea what is happening when the rogue or scout or other loner is getting mauled by an owlbear or smothered by a mummy.
Scout: "aaagh, I'm getting killed by a troll, help!"
Rest of party (in another room down the corridor): "Did you hear something? Nah, must have been my imagination."
Scout: "C'mon guys, it's a DC -10 check to hear a battle, and it's only 60 feet away through a door, that's like a total of DC 1 to hear! And the DM says that my screams give an ad hoc -2 to the DC! If you roll a zerp you can still hear me!
Party: "sorry, we count as distracted. Plus you are the only one with ranks in listen...."