X-Com 1 and 2 (new versions) are great games, even if they moved away from the large squad slaughter that was Enemy Unknown, terror from the deep and partially Apocalypse. I personally really enjoyed looking at black sections of the map and thinking "that will cost 3 rookies to explore"
Everyone is aware of the "95% to hit meme" around X-Com, and if you've played Phoenix Point, the difference is especially jarring. If you haven't, aiming in that game is purely a probability cone, so standing point blank next to an alien means something. In X-Com it doesn't mean diddly squat.
I finally figured out what the problem with X-Com is, and why it's always uniquely frustrating. With it's pod based mechanics, fake stealth and drip fed enemies. What you are seeing on screen has no relevance and only serves as a distraction. Being right next to an Alien and missing is irrelevant because where the character and alien are on screen do not correlate with the game.
X-Com is, for all intents and purposes a very fun card battle game. If it were a Dos prompt game, with exactly 0 visuals, nothing would be lost.
Try it next time you play, completely ignore the visuals and imagine your character as a card drawing a dice based attack against another card.
It does, but for the wrong reasons. Players tested the stealth AI, it hones in on your fireteam even when they are still in stealth. Mods exist to change this and maintain a more realistic patrol pattern.
This can still work for some missions once your Reaper is high enough in rank. Remote Start doesn't break stealth/Shadow for example, so hostile VIP missions where you CBA to kidnap the target become extremely easy if the VIP is next to a car and also within LoS and range of the evac point. You can move all the way to the evac point then spend your last turn setting off Remote Start and then hitting evac.
It's options like this and other facets of the Reaper which in my opinion make them both the strongest hero class out of the three, but also the most important class to have on any mission when things like Target Definition which lets you track previously seen pods through FoW and out of LoS. They don't even need to attack to be the MVP of a mission, simply feeding info to the rest of a fireteam with Target Definition or spotting for a Sharpshooter with or without Long Watch due to Squadsight.
If you really want to play unfairly you take 1 Reaper and 3-5 Sharpshooters with Spider/Ghost armour to grapple to a sniping spot and just lay waste to everything on the map the Reaper spots. The ship defense mission can benefit from this extensively since any custom turrets you build also have squadsight. So a Reaper booking it for the EMP device or Chosen cannon power source then has 2-4 turrets with 100% aim and infinite range against objects, aka both those objectives, as well as however many Sharpshooters you may have at hand.
tl;dr Reapers are the most powerful unit in War of the Chosen.
I'd probably go Reaper, Templar then Skirmishers in terms of power. Reapers have solo'd chosen and half of the enemy with their Banish ability
Templars were just great at running around, causing chaos and avoiding all damage after
Skirmishers were ok but to be honest they were on par with mechs on terms of damage they could do.
Reaper supremacy!
Plus they, which included Troi, were led by Riker while the others, which included Worf, were either led by Tasha Yar or Q.
Templar will carry you hard for the first half the game between their guaranteed hit melee and their one ability to deflect any one shot at them after a kill. By the time they fall off, you have your other units ready to get the slack.
Considering the early game is the hardest part by far, I'd lean towards Templar being the most powerful in general terms as they provide something concrete at a time when no one else can reliably do so.
Reapers are capable of doing some wild shit and cheesing the fuck out of the game, but by the time they can do so you probably have many options at your disposal. And they rely heavily on the, as you said, broken Stealth system unless you mod it.