Heimers turrets need to shut down the moment he dies.

I disagree. The way these turret works is from heimer's mind and we all know that when you stop breathing and your hearth stops beating your brain remains active for 4 more minutes which explains why the turrets are still active for a short time after his death

Then Heimer becomes hilariously easy to dive.

Uh thats the point. If heimer wants to engage you he has to have a couple of things

All his turrets up

3 seconds to even get all of them down

You have to LITERALLY STAND STILL while he puts these new turrets around you

If you fight a heimer within his zone aka diving him under a make shift turret. Sorry thats just kinda your fault. Ignore heimer dont kill him.