Whenever on field you get a lot of snipers heading for the concrete blocks. We think that from the firs block you can get to your artillery. They can pick off your engineers quickly and if there are enough of them they will destroy your vehicle before your engineers get back. If you try to shoot at them they will see your shell a mile away and by moving back a metre or 2 are unharmed by it.Another counter to your tactic is that someone could quickly run around that corner and plaster you with c4.
You're all right, it really comes down to teamwork.