AI Tank gunners seem to have a few problems
1: They fire before they have the target in their sights
It is very easy to reproduce. Place a tank and make an enemy vehicle appear some distance away from it. The Tank will turn the gun and fire before he finishes turning. The first shot will always miss.
2: Ai gunners turn the turret extremely slow on the last few degrees.
This is also very easy to reproduce.
Place an enemy rifleman and play as the tank commander. You will notice that the gunner is [B]extremely[/B] slow on the last few degrees while turning the turret towards the target. Because of problem #1 he will already begin to fire and waste at least 50 rounds before he starts hitting the enemy.
I guess that both problems are linked to each other.