I have just completed the game on Legend with NJ, having previously completed it on Hero with Anu and with Synedrion on Veteran.
Since my second playthrough I have been playing with increasing self restrictions to avoid First Turn Strikes (an overwhelming attack on the first turn that decides the engagement, leaving the opponent without any real opportunity to win before it even had a chance to move) (FTS).
For my last playthrough on Legend, I limited each skill use to once per turn per soldier (and Rally the Troops and Electric Reinforcement to once per turn per squad), did not use Frenzy, soft capped Speed at 20 and not cast Rapid Clearance before Adrenaline Rush.
Overall, this worked reasonably well most of the time to avoid FTS, though by the very late game (I finished in early March, game time) my veteran soldiers had the full skillset, and maxed out stats (except Speed, which I kept at 20) and the Pandas never stood a chance.
Of course, the first problem is the prodigical flood of SPs that by its own momentum turns the veterans into Terminators by late game (incidentally, of my veterans only 1 was from the original 4 - the other 3, and many more perished along the way… ). This fundamentally inverts the difficulty curve, more so on Legend: a moderate to hard start is followed by increasing difficulty, until reaching a peak somewhere just past mid game, after which the difficulty suddenly plummets. It’s the old XCom curse, just worse.
The second problem is that the above mentioned self restrictions still allow for some powerful combinations, such as Biggest Booms and explosives (particularly the Thor and Ragnarok rocket systems, but also just grenades with the Quarterback perk and Ready for Action), and Phoenix Point laser PDW with Rapid Clearance and the corresponding third row damage buffs (a build which works similar to the assault/serker Rapid Clearance + Adrenaline Rush combo with AR, except there is no need to cast Adrenaline Rush).
However, an additional issue that I see is the enemy deployment, which, particularly in the last missions, makes FTS unavoidable and terribly effective.
The thing is, deploying large number of enemies to increase difficulty in the face of FTS is putting out the fire with gasoline. The last NJ story mission, as well as the final mission, are prime examples of this. They are over before they even begin, because those enemies that survive the FTS are panicked from the loss of WPs occasioned by the deaths of their comrades.
Now, I’m coming at this issue from the “game is too easy on Legend because of FTS”, but the same argument can be made in reverse - “the game is too hard on Rookie if you don’t do FTS”.
I didn’t notice any difference in the last missions on 3 different playthroughs on 3 different difficulty levels. This doesn’t mean that there aren’t any - there could be double the number of enemies, with more HPs and layers of armor; it means I didn’t have a chance to notice anything about them before I wiped them out. In other words, increasing enemies, or their stats won’t increase the difficulty. On the contrary: for FTS, filling the map with enemies like sardines in a can only makes it easier.
Thus I would like to submit the following for discussion and consideration:
Reconsider the deployment of enemies, avoiding their placement (especially in clusters) within easy reach of the player. The player should as a rule start on one edge of the map and the enemies on the other, without LOS between them.
Add more and more types of dormant, and hidden, enemies, for example Arthrons in cocoons, that will activate when either they, or connected Pandoran security systems are disturbed by the player.
Use Pandoran reinforcement points more extensively, perhaps giving advanced warning of which point will spawn the next wave of enemies.
The 2) and 3) could be used to modulate difficulty, so that significant numbers of dormant/hidden enemies and reinforcements would only appear on Hero/Legendary.
This would also smooth out the difficulty by making early detection by enemies less probable, which, you know, leads to entirely predictable and legitimate complaints about Chirons…