RA is good but not 100% effective, one of my callies survied 3 RA attacks thanks to field repairs, it was killed by the 4th, but I had 2 callies more anyway lolz.
I stole a Flak today, the defender used RA twice to get it back, not once was to de-crewed but was destroyed in the end, mainly because we damaged it taking the thing. Rocket arty today has been full of fail, one was even used to kill my Vet3 Engineers, they walked out of it, built a triage and healed themselves before going flamo-mental elsewhere. Rocket Arty is not expendable, you need to get it exact to be of any use.