Worries me too Don. That mind set might give you comfort in that you have a particular scenario in your head and you've already played out the roles with the actors.
In reality that Thug, In economic terms, as calculated the cost/benefit ratio risk/return in his head and has a game plan and is actually fairly surgical in his attack. Don't confuse it with skill, as he may have none other than suprising you and overwhelming you with whatever to get to what he wants, acheive his objective and exit.
If you can weather his attack, regroup, and turn the tide in your direction...that is the key IMO and something we probably need to practice over and over from positions of failure.
Counting on him being off balance, in a rage...yeah...sure, that is one scenario for sure...but it is jus that, one scenario.
Amen...I think you hit the nail squarely.
To anyone interested in the topic of self defense, I highly recommend a book titled: "Meditations on Violence: A Comparison of Martial Arts Training & Real World Violence," by Rory Miller.
The author is a prison guard who has significant experience with "street thugs" and insists that these type of attacks are almost always faster, harder and more surprising and coordinated than we could anticipate.
I'm no expert on the subject, but I think this is why it's important to be able to take a shot or two without freezing up.