I still not sure why you are so hard on 6th sense, I have it on every tank and it saves me from arty all of the time. As soon as the light comes on I know I have about 5 seconds to get moving. I also find it quite useful on arty, as I know when I have been spotted by a scout and when not.
Two reasons I'm not huge on it. First, there's a delay from when you're spotted to when it lights up. I've been hit multiple times before the thing even goes off. I had a game in my Bat Chat the other day where I was scouting a ridgeline, Sixth Sense went off, and immediately a good player in an enemy arty hit near me. There's limited routes to scout on many maps and this guy was just waiting along an expected one. Sixth Sense didn't really help me there.
Second, it doesn't tell you when you're no longer spotted. I've counted down before after it was lit up to the point where I should no longer be visible, moved to a different firing position, and been hit without Sixth Sense going off. Obviously a second guy had me lit slightly after the first to the point where I remained lit up by the time I moved back up, or he never lost track of me, or he had the perk that kept me lit up longer.
I've come to appreciate its value in competitive play, though. With comms and a team that works together it's invaluable to know what tanks are lit up and which ones aren't. It helps paint a picture of likely enemy movement and you can then react off that.