I'm responding, not because I own the Kharkov game yet, (it is on my top 2 hit list, though) but because, I too tend to be overwhelmed by larger scenarios.
I am however, currently playing a couple of large scenarios, including `Battlefront: Market Garden', and `Across the Dnepr'.
The approach I've taken with these is I treat them like a `work in progress'. In other words, I don't spend an entire evening of free time playing one. Rather, I'll make a turn or two, and then do something else. I have to say, the larger scenarios are very rewarding, and help you learn a lot about the SSG systems, which I think are the best of the hex based type games. I own Korsun/Dnepr, Battles in Normandy and Battlefront.
I do perceive that, at the very least, the new AO system will create a more focused approach to planning and at least to that extent alleviate the feeling of being overwhelmed by a large scenario, and dealing with dozens of units.
I hope this feedback gives you some ideas.