Your question is strange. 'Send a Tech to kill a vip' ? Your talking about the missions where the vip is next to a car in the cities? You should never kill the vip's if possible. Why would you have one less man available ? Your sending in a team to extract the vip surely ?

"Your talking about the missions where the vip is next to a car in the cities?"
Yes
This is a mission to capture or kill this enemy vip. It is much easier to kill him than capture him. You can easily kill him with just 1 soldier, that being a tech and using his rocket.

But then that solo soldier has to survive vs 8-15 enemies on his own ! Surely you don't send soldiers out on one-man missions.....You gain intel usually from the captured. check the screen after the mission. He gives info after interrogation I'm guessing. Anyway you need missions like this purely to gain soldiers experience.