I lost hours figuring this out. Just because the Devs at Magento aren't capable of making an understandable configuration, or yet even documenting their code in a way a human being would be able to read it. 

This part is just a random name. you just need to make sure its unique

    <admin_adminhello after= ..... >


The _Adminhtml must be added to your module, to tell magento to check the folder 
myNamespace/myModule/controllers/Adminhtml

    ... >Pulsestorm_Adminhello_Adminhtml< ....


Now the real Problem. Using the other (better) system you had your own namespace defined by using the "FrontName" Tag. You don't have this luxury any more, so you need to make sure your controller has a unique name. 


So I'm afraid you'll have to change your URL to
> localhost/index.php/admin/adminhellobackend/index/key/83f08ec4bddff37e47412e16acc8d3f6/

The File must then be stored as you already had it

> /app/code/local/Pulsestorm/Adminhello/controllers/Adminhtml/AdminhellobackendController.php