XCOM 2: Alien Hunters Review (Three-legged Wolf)
Like many have explained and pointed out, the ennemies from this DLC are stupid-hard to deal with. It gets easier once your squad is decently outfitted but it remains an unfair challenge despite this. I don't mean that these bosses are unbeatable since I have in fact taken several of them down, but just like a bad case of food poisoning, being able to live through it doesn't mean it's fun.
Early on when they first appear they can completely wreck your squad, and by the time you dealt enough damage to them so that they teleport away, your squad will be in a pretty bad shape and resulting in mission failure if you're unlucky. Since you can't kill them in a single encounter they will keep popping up sporadically to ruin your day on a later occasion. The thing that makes them so unfair is that they have "ruler reaction" which means that for every action one of your squadmembers makes (reload, move, shoot, etc), the boss will have a counter-action. Meaning that by the time you move + attack with 2 squad members, the ruler will have been able to act and attack 4 times. If you have 6 squad mates, that means the boss will be able to act/attack/move 12 times in a single turn because each time an action is played by the player, the boss reacts.
Compared to the chosen who can ruin your day when they appear and throw a wrench in your plans, you can actually feel like it's fair, they play by the same rules as your squad members. They have 2 actions per turn and are a big threat. These bosses by comparison play with godmode enabled.
Again, they are defeatable... but they suck, the loot they give also sucks and everything in this DLC is a waste of your money and time. I love XCOM, but the devs should be scolded for this addition.