From the quoted article:
To be clear, fault does not lie with the MRAP, MATV, or any other armored vehicle. It lies with how commanders are using the vehicles due to their aversion to risk and their attempts to minimize coalition injuries at the expense of the broader counterinsurgency mission. The vehicles' size would not be a hindrance to that mission if junior coalition commanders were also authorized to use other smaller vehicles to access the difficult areas of Afghanistan. For example, if a unit needed to access a village that was only accessible by pickup truck or Humvee, then that is what they would use.
Not sure about this.

Given the number and (blast) strength of vehicle IEDs in Afghanistan I would suggest that if troops need to travel or deploy by vehicle they need to use MRAPs... and then only the latest upgraded versions. As IEDs account for the majority of KIA and a larger number of really severe mutilation injuries it would be criminally negligent for a commander to send troops out in a non MRAP vehicle unless for a very specific once-off purpose.

It has been said that the Northern Ireland IED threat was largely defeated through the intelligent use of helicopters and the judicious use of vehicles. If the US does not know this then the Brits obviously do and they should have known better themselves in Afghanistan. There is no excuse for this.

I wait with baited breath to hear how sending troops down mined roads in unprotected vehicles will contribute to the "counterinsurgency mission".

Risk aversion is a problem in Afghanistan, I agree, but not in this case.