On what should have been done that wasn't:
The entire area beyond Regal cinema (near the Taj Mahal hotel, Cafe Leopold, Nariman House) should have been cordoned off. The media should have been kept away. All the guests that had managed to leave should have been collected and debriefed before released. Their names, (phone) numbers, fingerprints should have been taken.
The people who should have done this are the NSG's Special Ranger Group, they should have extracted whatever information was possible of what was happening inside and passed to those who were planning it on the ground.
During this planning period, somebody would give them the plan of the hotel, information on how many people were inside, CCTV footage if possible. Then a strategy would be formuated jointly with the senior committee.
They could have dropped MARCOS/NSG with choppers (helicopters). It takes exactly 5 seconds to drop a team of 8. A team could have landed on the roof without them knowing what had happened.
Once you know there are 2, 3 terrorists, you could slink NSG/MARCOS from other entries because the terrorists would not be watching all entries at all times. Since it is a massive building, you can insert cameras through hydraulic drills to know the movement of the threat.
On footage from the Mumbai police showing that the terrorists were in two rooms during the early hours at the Taj:
Then the NSG was not required, it was well within the capability of the MARCOS to take out terrorists sequestered in two rooms. The operation would have lasted exactly two hours.
If this information existed, it hasn't been passed down. These people don't have a response mechanism. Does the government of Maharashtra have a team that is immediately convened in such a crisis?
Image: An NSG commando rappels from a helicopter onto the roof of Nariman House. Photograph: Phil Smith/Reuters.
Also read: Did any terrorist escape?