In terms of safe zones, I mean places where I have better angles. There are some spots on each map where there are too many angles for me to cover, so I try to get out of them as fast as possible. That brazilian slum map, for instance, has certain alleys where you can be attacked from multiple levels above as well as front back and sides. Maybe that is the difference between my skillset and yours, because I know I'll be dead quickly if I stay too long.
In terms of perks I only use cold blooded on hardcore mode. On softcore mode I always use stopping power because I want to drop the enemy as quick as possible. Yesterday I played a round on hardcore where everyone had cold blooded. I dropped my sentry and it never fired once. I saw two harriers come in and they flew around a while and I only saw them get one kill. It is a useful perk, but I wouldn't trade the damage of stopping power on softcore modes. As for ninja, I find it's helping me, but I haven't even looked at my other options in that slot in a while. I know I got last stand, which would probably get me some kills.
In terms of perks I only use cold blooded on hardcore mode. On softcore mode I always use stopping power because I want to drop the enemy as quick as possible. Yesterday I played a round on hardcore where everyone had cold blooded. I dropped my sentry and it never fired once. I saw two harriers come in and they flew around a while and I only saw them get one kill. It is a useful perk, but I wouldn't trade the damage of stopping power on softcore modes. As for ninja, I find it's helping me, but I haven't even looked at my other options in that slot in a while. I know I got last stand, which would probably get me some kills.