Tips for playing the Sturmpanzer II?

I really want to be decent with this tank(tank destroyer? artillery?) and I've seen nothing but praise for it while searching for info about it, but the only thing it has going for it is the huge gun, which usually one shots people if it does hit anywhere, but it's extremely difficult to get on target and hit anyone. It's slow as a snail and even slower to turn(so being flanked means 100% death).

• The gun velocity is terrible so sniping is out of the question, even medium range shots are difficult.

• It has an open top and is vulnerable to machinegun fire, AA fire and artillery.

• It has somewhat alright armour against regular tank shells but that's irrelevant as anyone with a machinegun or HE shell can kill it.

• It has a long reload, so if you fire and miss the enemy now knows you're there and you're dead before you can get another shot off.

• The gunner is usually the first to die whenever you get hit, so if you do survive a hit you're dead anyway because you can't fire back(and escape is impossible due to it's poor speed, acceleration and turning).

• Gun depression is nonexistant, so the enemy has to be straight on or above you to be able to hit them, if you're cresting even the shallowest hill you can't fire until you're in an extremely vulnerable spot.

I find that I pretty much have to get into close range to do anything with it, but unless I get the drop on an enemy(hard to do when my vehicle is so slow that they're gone by the time I get into a position to attack, and I can't fire from any kind of range, so usually have to move in closer) I'm pretty much dead. It seems like it would be useful as an artillery piece if we actually had some kind of artillery aiming function that allowed you to aim over obstacles properly.

So am I doing something terribly wrong or is this vehicle just bad?