Some other thoughts...
Lets look at Static Heavy Bombardment Artillery as Anti-Vehicle AND anti-personnel weapon.
Static, Light Armour, Heavy Bombardment; 3 shots, 20 AP, 60 Damage with 10 Armour and 30 Hit points for 1.44 cost.
You get to build 8-9 of those for a single heavy tank.
lets say roughly 26 shots at AP 20 for 11% penetration chance per shot at 2.86 penetration per turn. At 60 damage that is three tanks dead. Even if the front is low on tanks these artillery pieces are not that bad against other stuff.
Static, Light Armour, Medium Bombardment; 3 shots, 15 AP, 30 Damage with 10 Armour and 30 hit points for 1.04 cost.
You get roughly 12 of these.
So 36 shots for 2.25 penetrations and 1.12 killed tanks... less effective heavy tank killer but slightly better at killing infantry if they have low armour.
Vehicle, Light Vehicle armour, 2 Medium Anti-Vehicle cannons; Size 82, 2 Shots, AP 40, Damage 60 for Armour 20 and 40 hit points and 3.28 cost
So... you would only put these forward on the front line when there is a sizeable chunk of enemy tanks and not a huge amount so they are rarely targeted.
You get roughly 4 of these anti-tank assets.
8 shots at 44% penetration is 3.52 hits and kills
A medium/heavy vehicle with 2/3 HCAP would be good when for assault...
Vehicle, Light Vehicle Armour, 2x HCAP for 2.58 cost. 40 Hit Points and 20 Armour.
Heavy Vehicle, Light Vehicle Armour, 3x HCAP for 3.86 cost. 60 Hit Points and 20 Armour.
Both of these are cheap enough to go on the line and not too big to be immediate target if in decently small numbers.
The medium one will have roughly the same amount of shots as the same cost of power armoured marines but AP 20 instead of AP 10 thus more effective at high armoured targets. But then again why not use HCAP Marines instead at 0.8 cost, I get three to four of those for each vehicle. If they have Armour 30 they cost 1.2 but are allot more difficult to kill for regular infantry and I can use a higher mix of them in the army.
And as said going to 30 Armour with infantry is a big deal for their survival-ability against all infantry weapons... against vehicle weapons it does not really matter much because big vehicles are so damn expensive anyway and kill very little Armour 30 infantry, even with HCAP weapons. I still get roughly 42 Heavily Powered infnatry for 1 Leeman-Russ battletank... or better with 30 Marines and 3 HCAP marines for each tank. I would probably not be afraid to go even a ratio of 8 Marines and 2 HCAP Marines... sort of squads of 5 with one HCAP in each one...
If the enemy have a strong tank presence then add a squadron of Anti-Tank vehicles for each company, otherwise just keep them in reserve.