If you are close enough, a gold shell to the "cheek" of the turret is much more reliable. Sniping the hatch with gold shells is... not the best idea because of the weird angle on the hatch. You can also shoot the "top" of the gun mantlet, the part where it doesn't overlap, if your gun is good enough.
I've also been damaged by getting shot through the gun. /shrug
And to add to what you said, this is why i rarely back off in a T-29. Once you move out of the way, you've lost the most important (and strategic) part of you hulling down. Which is also why i hate arty.
Not sure why you spam HE to the turret hatch though. What's the logic? The tank only takes like 100~ damage from 120mm+ HE rounds, less if it hits the mantlet.