I didn't try out the endgame stuff until the very end here. I think the imbalances of the early game are gone in the endgame. I felt things were wildly imbalanced in all the early game stuff, and largely in the DZ as well (although, a lot of the DZ is just you being on fire all the time...suicide bombers, flamethrowers with incredible range (and that seem to be able to burn you through trucks), etc).

The endgame mission, though, was a totally different and far more enjoyable experience. It was tough and challenging, but things definitely felt more balanced. The NPCs do seem to die more easily, and seem to be about as resilient as you yourself are. The challenge is that they use cover and skills like mad, and they flank before you know it. But I would rather have this difficult but balanced gameplay, than the very imbalanced gameplay of the early game.