This is far too harsh on ISDs 1 & 2. They have their flaws, but they get the job done, when you use them right. They work wonderfully in fleets with Praetors, Allegiances, Torpedo Spheres or Secutors. I've completed Endor Aftermath on Admiral as Eriadu, and I haven't lost a single ISD throughout the entire campaign. Just don't expect them to win battles on their own, always make sure that they have support (they themselves function best as support units for battlecruisers, imo), and micromanage pathfinding, so they don't turn their asses to the enemy. Trust me, it's all possible, and is much easier than it may seem.
Given his requisites, I'd definitely agree with the ISD-I ranking he gives. They're not worth building. They're not EXTREMELY cheaper than the ISD-II, but they are far inferior in combat. And they have absolute garbage fighter/bomber complement.
It could easily be argued (IMO) that the IR ISD-II should get a 3 instead of 2.5, and the Zsinj a 3.5 instead of 3, but I personally wouldn't be willing to argue for higher than that. Quite frankly, given their poor fighter complement for the IR, they're not fantastic. They're adequate, but given their cost and fleet cost, they're certainly not anything better than average. Their popularity in IR fleets is, IMO, more a reflection of the lack of anything truly better until you're quite rich than a reflection of the competency of the ship. Zsinj is obviously superior given their fighter complement, but they're still only an average or very slightly above that ranking.