"Or is your stance that a person committing robbery..."
Consider the crime of attempted murder.(IMAL) that's when a person attempted to commit murder but failed. So they had intent and action, they just failed
Armed robbery is someone whose intent is to rob someone and they are successful at the act of robbery.
The reason the robber is armed is not to harm the person but as a threat. If their intent is to harm the person that's an additional crime (assault, murder, attempted murder)
"that is highly likely to cause great injury or death?"
Highly likely for the robbery or if they carry out the threat. I believe the vast majority of robberies where violence was threatened don't end in violence. I don't have data for this so if you contest it I'll recind that claim.