I haven't played it, but some of the things that are happening in the Xcom playthrough don't even seem fair.
Not particularly. He had a run of bad luck with high-percentage shots in the first mission, but the rest is avoidable:
You need to think about not whether your soldiers are flanked when your turn ends, but whether or not they can easily
be flanked when enemy movement is taken into consideration. Pat puts his units into cover in positions where the enemy can easily flank them without even using a full move. That's just something you have to learn not to do.
As noted before, you need to recognize the difference between full and half cover. Half cover, especially when you're using unarmored rookies, is practically worthless.
Prioritizing Sectoids is understandable, but if you haven't modded their AI, it's actually better generally to leave them up and focus on killing another unit. They will usually create a zombie if a corpse is available (so, make a normal trooper/officer into a corpse for them), which is basically a waste of their turn if you can disorient or kill them on the turn that follows. (Pat knows to Flashbang them already, which is good.) Mind Control generally happens as a result of them either having already raised a corpse (putting it on cooldown) or not having a corpse to raise.
The conditions that break concealment are a bit more on the esoteric knowledge side of things, so it's understandable that he got caught off-guard by that, but they're generally very consistent and reasonable. The only thing I think is unfair is that he may not be aware that Dashing (ie, moving beyond the blue line with a single action) creates noise that causes enemies to patrol toward that location. (This is a mechanic I haven't actually seen explained anywhere that's actually really important.)
The place where Pat got screwed is not having a Concealment Ranger for scouting, which was ultimately caused by poor decisions in previous missions, so not technically "unfair" though it is a bit of a rough draw. A Ranger with Concealment starts out stealthed even if the rest of the squad doesn't, so you can use them to scout safely on missions like the VIP extraction. If you don't have one, you have to be far more conservative about your movements to avoid triggering multiple pods; basically, you want to try to slug it out and fight in place rather than advancing on enemies while they're still alive, because moving forward could draw more pods into the fight. (Though, on a timed VIP extraction there's an obvious Catch 22 in place, there, which is why it's so brutal to not have a proper scout for those.)