We were very good in Vietnam at rapidly constructing defendable firebases. The knowledge and background is there. With all the time we've spent (and are planning to spend) in Afghanistan, I'd hope we'd be breaking out those lessons from the past. There are basics of fields of fire, etc. This is not unique to Afghanistan. the history of small wars is one of small outposts or columns being overwhelmed by an irregular force who has the temporary advantage of surprise and mass. If you think in terms of raid, which was what this was, the Taliban acheived a period of relative superiority within which ti achieve its objectives, then withdrew as that window collapsed, as it naturally does (I'd recommend McRaven's SpecOps as a great read on the theory of raids--he's also the current commander of JSOC).
In terms of the tactical effect, from what I understand, one of the shortcomings was how long it took for reinforcements or external fire support to arrive. I'd be curious on the thinking that went into that planning. We can look at the situation in one of two ways: either the COP is to be rescued with reinforcements and fires directed at saving the perimeter itself, or the enemy massing is looked on as an opportunity, and we maneuver our reaction force and fires to cut him off from his planned withdrawal.
The latter option requires more flexibility in response, but is also has the opportunity to also turn the tables on the information/perception loss we suffered. As it was, even with the casualty mismatch, it appears the enemy not only had the initiative in engaging, but in disengaging as well.
s/f
Phil Ridderhof USMC