Finished Mechanicus.
I don't normally approach games trying to optimise the fun out of them, or uncover some kind of hidden strategy to cheese the game's mechanics, but in Mechanicus that was just so easy.
Once you kit out all of your techpriests with stealth items (which are incredibly cheap), you can just wander past most encounters without any issues, and fight enemies entirely on your own terms - they cannot detect you. Until the game suddenly arbitrarily decides that this "escape" mission is now a "kill everything" mission only after reaching the designated escape point (which is super annoying when it happens). Then you just mow everything down with your incredibly powerful AOE weapons, and cheese the action economy with a multitude of cooldowns which completely refresh your action points.
It was a fun enough time, but even playing on Hard mode, the difficulty just craters about half way through, after you discover some kind of somewhat optimal strategy.
The final boss also blew chunks. They are one of those dudes who relies on having other minions in the fight with him to be a challenge, but if you defeat them in their own separate missions beforehand, he just becomes a big healthbar with nothing else going on.