i never said the game gets harder as you go, just longer
for sure, fort joy is by far the most difficult part of the game, and by the time i was in the last act none of the fights (save maybe the final one) were a challenge at all
But IMO, that's just not true? The whole point where you outscale enemies to the point you nuke them down makes fights shorter.
If you remember some fights in Joy equal level in prison on the way to the boat, for example, or Voidwalken encounter before first time you go to Hall of Echoes. Those fights were WAY longer than just about anything you have in Arx, simply because you could not just nuke shit down at that point.
Fights easily get shorter as game goes on, unless you choose to make them longer for whatever reason it may be.
The seemingly impressive armor and vitality numbers NPCs get are no match for even greater numbers your nukes get, that's the problem lategame, which also makes mixed teams or advanced tactics waste of time and weaker approach IMO, as opposed to simply "lol kill shit" approach.