Recruitment centers are actually quite hard to destroy. I had 15 people sitting in one region to destroy one recruitment center and we couldn't accomplish that for 4 days.
This is true. With 15 people in the region for 4 days, it would have been easier to kill the entire population by looting. The enemy realm wouldn't have been able to use the RC for a long time afterwards anyway.
Also, if you manage to kill half the population, at least you've done that. If you damage 50% of a RC center, you really haven't accomplished anything.