(re: Deep Ones, Tasoths, Lobstermen)
Just some ideas here.
In my personal mod I made Deep Ones ToughAF but took away their Snap Shot. Flavor text says they have aqua plastics mesh on their skin so I gave them like Armor 15 and 90 Health. Not having a Snap Shot means you can dogpile gunfire on them as rookies and itll work, but it demands that you bring Extra Ammo in the transport. It also seriously reinforces making Double Sure you have good cover at the end of the turn - since you're not getting Deep Ones to expose themselves with snap shots you have less odds to know where they are (to savescum the foreknowledge) - and you will get surprised. And this serves to both slow down combat and get more civilians killed by aliens because you're pinned down. Immediate inspiration to get Gauss or Pulsers. And satisfying to have Sonic because you see them go down in 1-2 shots.
Did something similar to Calcinites too. Armor 30 and 130 Health and 70 TU. When you face Calcinites its a big wakeup call - did you bring Coelacanths like you're supposed to? Do you have heavy damage weapon capability? ...idea is basically its a blob in a captive suit so you're shooting jello, but eventually the suit gets shredded. To be nice I lowered their melee damage, but its not too much of a consolation.
I kinda see Calcinites as Xcom's version of Jason Vorhees, tough as hell, comes out of nowhere, and beats the hell out of you.
I gave Lobstermen about 50 Armor and shifted their protection to the armor rather than damage resistances. And kept them about as tough as they're supposed to be by the numbers. Guess
Tasoths get more dangerous for Late Game because weapons went to flatRate TUs so that means they actually get 3 shots with Blasta and 2 shots guaranteed with Cannon.
(24/39 TUs for Blasta and 33/43 TUs for Cannon, pistol went to 16/28 TUs)
Then again I also nerfed Tentaculats by removing zombie ability. But they can still screw you up just as fast, having senior officers die is no joke. Its still like 90 damage and ignores 1/2 armor and causes a bunch of fatal wounds.