I'm not exactly experienced with this game. I played a normal dif game about a year and a half ago and a normal game with Ironman and Dead is Dead before starting this one. Not sure what made me decide to attempt this single sniper expert run, but i was victorious nonetheless! (with lots of savescumming)
Early game was an absolute disaster. Naturally i took Rey as commander (i don't see how single exo expert runs are doable without him), but the first couple of missions still took me a number of restarts. Things got better once i got my sniper and laser rifle dmg up a little. I had no hacking points throughout the whole game. Instead i used a lot of virus, which really helped a lot. I've had many cases where i would have died if i didn't have some virus. Especially for Bodybots if i failed to position another bot next to it. I converted so many of those. Nearly played myself stuck a few times by having them run out of ammo in a tight corridor, with not enough bots around to take it out. Emptying all clips on it, committing suicide on mines and getting ammo refresh from Rey's revival was the answer in this case.
I avoided Lion's den and Assassination mission until my sniper had 2000+ dmg and my laser rifle 1000+, which was about after 30 missions or so. I was going to try to clear the game without getting the epic exo upgrade (which took me forever to find), but the Assassination mission i did at 18 days left was really quite difficult. At that point i decided i suffered long enough and just wanted to steamroll everything. 1 day later i got the upgrade and the rest of the game was a joke (finally an aoe gun!). The only time I'd ever die after the upgrade was when I'd commit suicide to refill ammo. Ended up with 10k+ dmg on the sniper, 25k dmg on the railgun.
Getting new items was tough in this game. I really had to get used to only getting 1 piece of gear after each mission. I got lucky with getting several of those cryopods missions early game though. No hacking points meant less loot but i don't regret my virus choice. Less loot to sell also meant i was not able to use the shop as much. 30 credits per kill near the end of the game was of more value to me.
My final score was 1,720,000 and i unlocked a whopping 34 achievements at once. I did not play with any special options, though i think i could have made it with Who Designed This Circuit. Next single exo run i do will definitely be something that starts with an aoe weapon.