In Insurgency 2, it was absolutely terrifying to run from cover to cover. Being out in the open, even for a brief second, could mean death. This meant that every movement you made had to be thought about. It required strategy just to get to the frontline.
Now in Sandstorm, because of the heavy armor TTK, I see way too many people with no regards for the way they are moving whatsoever. They're running over hills, across open streets, and straight to OBJ because they don't feel the fear and the pressure that was in Insurgency 2. This is the real problem with the TTK. High TTK means you can get away with more failures and mistakes. It means you can run around a corner, see an enemy, turn and run right back into cover without any problem (want proof? Check it out). The entire game changes with a high TTK.
Edit: I mostly want to know if this was an intentional decision by the devs. They need to be forthcoming if they felt like the one hit body kill was too fast in INS 2 and if they decided to change it in Sandstorm.