I'm on Tier 33 now, so it's switched to Extreme mode. I have all Rebel skills maxed, and this is where they come in quite handy. I'm finding Spotting is quite useful since on Extreme you have no orange clouds to indicate unmarked enemies. Calling in rebels and raining down mortars, as well as using diversions is generally plenty sufficient to overcome any base if things go sideways on you and you have to go loud. It's especially safe if you find a good hiding spot to use the drone from, like inside a concrete pipe.
I'm not really doing defend the emitter missions anymore, since I have all reb skills maxed. Last one I did was in a eastern level 3 province. The emitter was set in what looked like a parking lot of a L shaped motel. Waves of armored vehicles, helis and foot troops came. I died and had to retry several times. I finally got it by staying prone in the front corner of the parking lot where there was heavy L shaped concrete to stay protected. I just kept taking out helis with the Desert Tech HTI BDC, calling in rebels, and mopping up fot troops with my assault rifle.
Now I have only level 4 and 5 provinces left, and am finishing up the level 4 ones. I'm kinda cheesed that they apparently tweaked the EMP so that convoy vehicles don't stay stopped by it anymore. I've sufficed with an armored vehicle drop, taking out escort vehicles from afar with the Desert Tech HTI BDC, then going after the target vehicle with the AV's mini gun and ramming it. Once you get good at the ramming they can usually be stopped without going on a marathon demo derby.
I'm still a bit upset they couldn't even get the GoTo command to work well, which would have made using your squad a lot more effective, but it is what it is. Still having a lot of fun, I just wish when I see this new DLC coming out they'd consider fixing a few main things they left broken in solo play.
BTW, anyone know how Diversion actually works? I can see a spot appear where I place it, but I don't see any rebel troops show up there, or any smoke, explosions, or other diversion element happen there, so what gives? Is this another broken game feature?