That is pretty much the nature of ANY rear tine tiller. I bought a used TroyBilt Horse at auction several years ago. I learned REAL quick that you DO NOT attempt to go full depth the first time over. In fact, it takes several passes to progressively get to full depth.
I wore that Horse completely out, so I replaced it with a brand new Craftsman rear tine tiller. It behaves exactly the same as the TroyBilt.