I think it's intentionally like that so that they don't get sunk easily when transporting from Spawn. It's a pain, but you just have to keep distance from the grenade launcher's accuracy and hope somebody else will help you take it down too!
Makes sense, but it still seems to be far too hard to destroy, and it doesn't help that the majority of randoms on servers, don't work as a team; so you often end up being the only person trying to blow it up - last night was hilarious, team meats just left the things sat at the flag and couldn't work out where the constant flow of enemy were coming from.... ermmm..... it's a mobile spawn point
