As indicated earlier I'm now involved in the production of super-alloys (Ni & Co based as opposed to Fe based) but the processes are identical. During the casting of alloys it is possible that pockets within the cast ingot have different concentrations of the constituent elements which would lead to differing properties (strengths etc) throughout the final product - not good in any application. As a result all our ingots go through a process where, once cast, they are re-heated to temperatures that get close to their melting point and held there for a substantial period of time. This allows the elements in any pockets to disperse evenly throughout the metal and thus giving consistent properties throughout the end product, a process referred to as homogenisation. I don't recall this being employed in the production of armour plate.
I'm not sure that, due to their large size, material type (i.e steel Vs nickel), production needs, etc. that the cast armour bodies/turrets would have been homogenised in a similar way. Similrly I'm not 100% certain the hardnesses usually seen with armour plate can be achieved with cast armour. It is the rapid quenching from hardening temperatures that fixes the steels structure in the hardened & stressed state, followed by tempering which reduces the stresses, in plate of costnt thickness this is easily controlled, in castings of varying thicknesses not so. Add to this the already brittle structure of the cast (i.e. non-wrought) material probably explains why the early castings were poorer performers than later ones.