Given the article graphic, I was hoping for some mention of Shadow of the Colossus, which is, arguably, nothing but boss battles with all the fodder between removed.
One thing that sticks with me about that game was how inevitably, one could not use a single tactic to defeat a colossus. In the context of more conventional boss battles, this is also often true, a contrast with the usual minion which is is defeated by some singular (or eat least simpler) tact.
A boss battle, properly handled, thus represents an real test for all the separate tactics one has learned. Of course handled poorly, it breaks the tactical patterns too much and seems out of place with too steep a learning curve. I can think of examples of failure in this latter regard in stealth play that suddenly decides when its boss-fighting-time to abruptly go full melee, even though the prior play actively discouraged such engagements.
ALternately, there would be other extreme: the success where the boss is a fluid organic escalation of the minion battle such that gameplay simply transitions without pause or experience of the common "oh, here comes the boss fight" moment.
Which brings me back to SotC ? which pulls off much of that fluidity without a single minion, where the seamless movement through the environment is the preparatory experience.
