Hello, at second attack I send bomber at first wave, on his line be 4 buildings with 1% durability and Construction Yard with full durability, so bomber with almost 100% of durability did only bit dam...
I have 14/14 units types in attack group, so I have space only for one Vendigo :) Vendigo have small durability, so I can use him only in last wave, when I finish (or almost finish) with destroying AA.