I'm A Banana
Potassium-Rich
If 4e was "everything is core," I imagine 5e will be "anything is core." 
Military tacticians throughout history would have some words with that. Fights in war or between people or even in nature happen most often when they are resolved quickly, and frequently between people of vastly different skill levels. If a fight lasts 15 minutes, someone done messed up.
Instead of zooming into the micro level of the encounter and seeing challenge and tactics there, it might be more worthwhile to zoom out to the more macro level of the adventure, to see a broader swath of possible strategy and tactics.

Hussar said:If a combat lasts for 15 minutes, why did we bother in the first place? It obviously wasn't a challenge to the PC's, there were virtually no tactics being used.
Military tacticians throughout history would have some words with that. Fights in war or between people or even in nature happen most often when they are resolved quickly, and frequently between people of vastly different skill levels. If a fight lasts 15 minutes, someone done messed up.
Instead of zooming into the micro level of the encounter and seeing challenge and tactics there, it might be more worthwhile to zoom out to the more macro level of the adventure, to see a broader swath of possible strategy and tactics.