It's as simple as this, no matter what lane you are in, you should be doing at least 5-10 mph faster than the vehicles to your left. At that speed differential it should only take a few seconds for you to pass the car on your left. If you're close enough to their speed that it takes you more than about 10 seconds to pass them then you either need to speed up or get over. If a slow moving vehicle forces you to change lanes you should accelerate as quickly as possible to match the speed of the lane you just entered. Whether the person behind you is breaking the law is not your concern unless you are a police officer.
The problem occurs because someone will get in the second lane from the left and do 70 mph while the flow of traffic in the left lane is 80. They will come up on someone doing 68 and get over to pass but insist on maintaining the 70 mph they were doing. They argue, much like you, that they are already over the speed limit so they shouldn't speed up to match, those crazy speed demons should slow down. Now they're doing 2 mph faster than the guy next to them so it takes miles for them to pass the car and get back over. While they're hanging out in that lane traffic piles up behind them and people start changing 2 or 3 lanes over to the right to get around the rolling road block you've created and then come back over. This is where the danger comes in.
I live in Atlanta too, and you are correct about needing every leave during rush hour, but outside of those times there's no reason for being in the left lane driving slow. The biggest problem during rush hour is people hanging in the left lane too long, getting really close to their exit and then literally stopping in the left lane waiting for someone to let them over to their exit. In reality, of everyone drive properly there is absolutely no reason why the left lane should ever stop, but it does, constantly.
Bear in mind that my comments are in relation to a multi lane highway. If there are only two lanes going in your direction the rules are different, but if there are 6 lanes, there's zero reason to get in the left lane if you are in any way concerned about your speed, rush hour wall to wall traffic or construction excepted.
One more thing I'll add to everyone. Please put your phone down and pay attention to the street signs while your driving. More and more I've noticed that people appear to have no idea what the speed limit actually is.
Cook, you just gave yourself away as being a bit guilty of this because you said you were on 285 and it was a 55 zone. About a year ago they installed variable speed limit signs and since then the speed limit on 285 is now 65 during normal times, so if you're doing 70 you're only 5 over, which is WAY too slow for the left lane on an interstate. Interstate travel is typically about 15 over on average, so if you aren't doing at least 80, your tires shouldn't even touch the left lane. There have been a number of other speed limit changes in the area, such as a raise from 55 to 65 on 85 and 75 north of Brookwood.
I knew someone local would hit me up about those new variable speed signs. I do my best to NOT get on 285 so I have only seen them a couple times and yes, they were at the time set to 60MPH. It was an example
Most people on 285 rarely do the speed limit including me as that is dangerous.
As for speed limit changes, PIB changed from 55 to 45 a couple back and out came all the law officers to take full advantage of that change with often 3 to 4 speed traps along my path to work so I do the posted 45 or really close as Duluth officers really are known for handing out tickets. Most locals know this and do the speed limit now but there were many days i saw a large number of people on the side having their credentials checked and an award handed to them. In visiting a relative in Mobile AL, I was informed to make sure not to speed as they have a zero tolerance policy and will ticket for 1MPH over. I was actually followed by an officer for several miles being out of state. I know he was waiting for me to go over. He eventually moved on.
Leaning back on my early schooling on limited access highways, there are several things that make them safe to travel on at a high rate of speed.
1. There are no directly adjacent lanes of opposing traffic.
2. limited access on and off and no traffic lights ( yes, why does the left lane ever stop moving SMH)
3. All traffic is traveling the same direction and here is the important part, at the same speed.
I am all for a giant homogeneous mass of traffic hurtling at 70 in a 55 ( or 60) zone or faster to keep changes in the traffic pattern and lane changes to a minimum so who are the evil doers in that situation when the few don't want to just do 20 over and drive safely with the pack and starts behaving badly, weaving in and out of traffic, causing people to jam on their brakes because they did a too close hole shot wanting people to move aside for them so they can get 5 cars ahead before they make a wild 5 lane across exit? I wonder who taught them to drive?
My goal when getting on a limited access HWY is to travel largely unimpeded and un-harassed to my destination just like everyone else. That will include riding in the left lane in accordance with current laws speed limit being excepted siting all traffic moving the same direction at the same speed as we are all a nation of law breaking speeders, the worst of which are most likely the cause of those type of accidents and not those obeying it at least in spirit. I do try and be courteous to fellow drivers and allow them to pass when I can move over safely but the left lane is inherently the safest place to be if you are traveling more than a few exits as it is the farthest away from those getting on and off the HWY where most of the lane changing and action is happening. I think the video has it backwards and that these rolling road blocks are actually also caused by those wanting to go faster than the pack speed and causing traffic disruptions by unsafely trying to get around adequately moving to suit their own need for speed. It works both ways. I have actually been passed by people on the left shoulder when i had no place to move over to and was unwilling to go 30+ over. I will add a caveat for cars in the left lane not doing at least the same speed as the other traffic around them but it should not require you be faster situationally. The less that cars around you change position in relation to you, the safer it is to move at speed. Some people simply need to slow down to increase the safety on the highways and yes, some need to just get in the right lane too.
If they put up speed cameras and aggressively enforced the speed limits on LAH like they do for the toll lanes without your Peach or SUN Pass, I think things might change but until there is some measurable consequence to these marauders, there will always be someone creating havoc on the highways by trying to go faster than the average speed regardless of rush hour or not.