Far Cry 3 regularly throws a lot of enemies at you in places with dense foliage, across wide open spaces... makes sense to give the player a better sense of what is going on. It also makes scouting out a camp important. If you have no way of tracking the guys with the miniguns, you may as well jump right in as soon as you have the opportunity to take one of them down vs moving on to check out the rest of the area.
The stuff shown here looks completely different.
I don't think having wall hack is a good way of having good sense of your surroundings.
You can still use your ears to hear them and I mean you even can throw rocks to move enemies into a location for you to kill them/ to have them distracted.
I have taken enough camps in FC3 to tell you that is really is not that hard without using it. Sure its more challenging than having the wall hack, but its a lot more rewarding and defiantly possible.
You can still scout and since the enemies have such linear/ easy to remember routes/locations it's also easy to remember exactly were they are once you move in to take over.
Either snipe from far, easy as it gets, or move in with a silent weapon and use stones when needed if an enemy gets close. Makes the game a lot more intense and makes enemies coming up to you a lot more surprising as you wont know they are near you.
Using the spot feature to scout removes any kind of challenge IMO, it makes going into the camp too easy as you know were everyone is ( like I said, without using it is still easy if you know what you are doing)
Being stealthy is not meant to be all that easy, The risk is getting spotted and fired on, which is almost non existent once you use the spot feature as you "know" this guy is coming as you see him through a wall.