I'm the anon that has been mostly building super-tanky heavy corvettes, and I started out with two Mk4 Lightnings, a Champion and a Leopard. I lost one Lightning along the way, cest la vie, but then the Champion just decided to delete itself. Okay, bloated savefile fuckery, I can manage. We killed off all the strike groups and most of the tactical groups on the way anyway, even if we only got a modest amount of Tarkhans along the way.
Then the Leopard got into a massive slugout with the Varyag, and despite launching 16 Zeniths at it, literally none of them managed to land a killing blow, and it suffered crippling damage. Needing an anchor ship for the north--eastern approach, I patched it up with emergency repairs and sent it out with an escort, and bam, it gets fucking nuked. SIX TIMES.
After that, it was a slow bleed of airstrikes, indiscriminate nuking and nothing with enough durability to stop the onslaught. It's a strange paradox, if you were to design a ship for Khiva. You want to be able to have the range and speed to respond to a crack in your defense, with enough armour to stop a cruiser or two that gets through your standoff weaponry, while cheap enough for you to be able to afford it at campaign start.