the "pak it to death" thing doesnt work against decent players. Try it and the bofors ability will cancel your try, it is more likely to lose that pak....
What always works for me and my mate is Fortification Doctrine for the arty- strike + sth. that gives sight on the Cancer
Only if your micro is somewhere at the bottom of the ocean.
You can easily hear barrage ability and it takes like 6-7 second for shells to drop. It's enough time t move paks few meters and attack again while barrage is on cooldown.