Nothing fancy, just some stuff I've learned after playing this game too much.
I remember a discussion with one of the devs talking about how the mobility/speed of AT guns must be carefully balanced. AT guns are potent in their current form.
I've been actively testing gun emplacement, timing and effectiveness. Enemy armor is a terrible thing to behold. Always, there are players running around screaming "AT! AT!", as their teammates are blown to bits. Tanks are death machines and I treat them as such.
Quick advice on how to stop those enemy tank crews from having so much fun:
IMO, AT guns are most useful when building them to quickly destroy an active and relatively immobile tank. In other words, a tank that you actually see, or a tank that is marked. I see a lot of AT guys building guns in anticipation/hope of destroying an enemy tank that happens to pass by. This is valid, but AT guns are cumbersome to traverse and "getting lucky" seldom works, in my experience. Lately, I've almost exclusively been building an AT gun only if I have an active target to fire at (yes, strong points are juicy targets, too).
It takes a little experience to quickly find an ideal spot and to properly position the gun.
The number one most important thing to do when using an AT gun is make sure you have all your team markers set to 500m.
Find a secure position and angle the gun directly at your target. Try to center the barrel on the optimal field of view. You can turn the gun as you're placing it with the Q and E keys. Position the gun in a secure area away from enemy fire, if you can. The farther the better. This is the most difficult step. You have to get it right the first time. The gun's effective range is phenomenal. Elevated positions are best. Elevation is shown on the maps, but it is hard to read. Low-lying areas are shown as groups of red hash marks. Obstructing terrain can be troublesome..."A Fence", if you will. Finding a good, elevated position is half the battle. Even slight elevation can make a huge difference for your line of fire.
A properly trained AT guy knows the value of the Support class. These two, together, can bring some serious firepower to the field. Support drops supplies, AT builds the gun. Both guys man the gun for the quick tank kill or bombardment of the hard point in prep for assault.
Cross your fingers and hope the enemy tank doesn't spot you as you send rounds at it. A tank will one-shot an AT gun and kill the crew. Enemy infantry will try to kill you. A few clicks later, hopefully, Dead Tank and/or captured point.