Their health really isn't different from the last version, their firepower got a little bit more compressed than intended with the projectile changes, but they're generally on par with the MC80B (far higher damage, but proportionally lower shields/hull), and somewhat weaker than MC90 (which is definitely intended) and way better than MC80s. The biggest difference is now the space above ISD is a lot more populated than in previous versions (ie Secutor, Allegiance, Bellator, Home One Type).
I actually got a chance to test an ISD vs. an MC80 earlier this afternoon. It was mostly a 1v1 fight with almost no fighters involved (one squadron of bombers on each side might've made a run or two, but that's it). The MC80 damaged the ISD's shields a lot faster than the ISD damaged the MC80's shields.
Here's the ISD: its shields are not quite two-thirds gone. Tavira's ISD isn't in range to fire on the MC80; this is still 1v1.
Here's the MC80: He's still got three quarters of his shield. Now, mind you, I think he just used his shield boost ability, which regenerated a bit of his shields and absorbed a few seconds' worth of damage from the ISD, but it didn't seem to be a drastic boost. Even before the MC80 used its ability, it was still doing considerably more damage to the ISD's shields than it was receiving.
Now Tavira's gotten involved and the two ISDs have worked together to kill the MC80. Two against one with no support, the MC80 died fairly quickly. However, the MC80 turned and went after Tavira before he died, and look, he managed to get Tavira's shields two-thirds down, too, even whilst getting double-teamed to death by ISDs. Now, maybe that is as intended. I know the lore says MC80s have stronger shields than ISDs. I thought MC80s kinda sucked against ISDs in 2.1, so maybe you've buffed them to make them more effective. If so, I'm glad you did, that's good for the MC80s, but I was just surprised at how quickly the ISDs took damage.