yeah...
1) Team Kill is not on. Makes a bit of a difference in terms of going all Rambo and making teamwork more of a necessity.
2) I've never been shot at... but I reckon if someone is firing an LMG down a small corridor, a) I wouldn't go running down that corridor. b) Popping my head out to try taking a shot, all those bullets coming at me would have an effect unless there was something wrong with part of my brain and I did not understand the finality of death. Perhaps there is some military training that can help people overcome that but someone more knowledgeable about military training can speak to that.
They will probably end up toning down suppression because people are complaining rather loudly but honestly, suppressive fire is a part of war is it not? It's SUPPOSED to encourage the enemy/opponent to keep their heads down so allies can do whatever they're going to do. It's called cover fire for a reason.
In this video, the enemy is largely running around like chickens with their heads off... that wouldn't yield much result with or without effective suppression. The arc of a well placed 320 would have shut him down pretty quickly from a safe position as he approached the escalators. Smoke is no guarantee but in some places can increase chances of survival and reaching a better position from which to get a good shot when it clears...
Suppression may wind up actually being too strong, but so far it seems people started complaining about it WAY before they could have really tried finding ways to circumvent it. That kind of negates the legitimacy of their complaints in my opinion.