The RPG is the most skillful launcher in the game. Depending on the part where you hit the tank, it changes the damage. Even the angle matters. A perpendicular angle hurts the most.
There are major zones like the front hull and front turret that are well protected. The RPG will do little damage in those areas. There are medium damage zones like the sides and rear of the turret, or the side of the hull.
There are vulnerable zones like the rear of the hull, the bottom of the hull or the top of the turret. There are even secret weakspots that become available as the tank gets damaged.
Knowing where to shoot and accurately shooting the tank, especially when it's on the move, certainly requires a level of skill.
So the bottom line is that if you are getting destroyed too quickly in a tank, you're letting the enemy hit you where it hurts. So don't get surrounded and angle your tank.
That said, I do fully agree that the RPG is overpowered right now due to the speed at which it flies. That's more an issue that affects helicopters the most though.