For SM players when they fix Assault Cannons many are going to realise how short on anti-tank they are (had to get that in). 
I'll say 2 anti-tank per tank. If you're SM for example it can depend on Power Fists / Chain Fists / Melta-bombs you have also.
I'll say 2 anti-tank per tank. If you're SM for example it can depend on Power Fists / Chain Fists / Melta-bombs you have also.