This has been addressed in canon. I'd answer but I don't want to get banned for addressing a point made by the mod staff again. That being said though, the Justice's size and class has been up for debate for some time now.
Not exactly.
"First Echelon, you're with me, blanket those cruisers, take ‘em out one by one. Second Echelon, keep those carriers busy."
This seems to me that the 2 Carriers were a WAY bigger threat than the first. Where as the cruisers could be taken down the carriers couldn't.
Fleet Admiral Harper (COM): "The carriers are breaking through, Sir! They're heading straight for the Cairo!"
Lord Hood (COM): "Cortana! Concentrate your fire on the first carrier. Admiral, do what you can against the second."
The Carriers were the ones who charged ahead. The cruisers if anything would want to hang back as a single SMAC round would end it.
The CAS is not a combat ship, Its job is to land troops and act as a command ship, can't remember where i got this in my head by they can only fire two of their energy projectors at once.