The cv should have been able to sit there and out cool your heat output, and had AT THE VERY LEAST 10 seconds of free run(more likely 15-20) not to mention the heat buffer. Also, since you mention dealing significant amounts of damage to the cv, it sounds like the cv armour bug was present, and fucking everything up.
Problem is this. Weapons now only need to heat the CV up to 20%, because his engine takes care of the rest. Once he's overheated, they only need to provide enough power for 20% of heat, and his engine (which is already at 80%) will keep it at a minimum of 80%.
Test cancelled due to armour bugs. Cv armour was way too low to test the new heat changes, and anti infantry vech mgs were just raping all vehicles...