Higher TTK means it's easier to get away from noobs by jumping 15 ft away and letting shield regen.
In COD, I dont care if someone is the best COD player in the world. If he doesnt use some good run and gun, camping or ducking behind cover skills, he'll get dropped in a fraction of a second.
But some people can still pull off being hard to kill.
It's 10x tougher to avoid being killed in COD than Halo.
Higher TTK in Halo also mean that in 4v4 structured teams moving in blocks of 2 will slaughter by teamshotting the 1000 K/D CoD suppahpro even before he could think about TTK