They took the factions that were on the verge of being overpowered and made them better, then nerfed the factions that were on the verge of being underpowered.
They wanted to make it faster, so they shrunk the map and doubled the base movement speed. That was a huge nerf to factions that relied on some kind of movement advantage as their strength: Guild, Fremen, even the Harkonen/Atreidis starting with a spaceport.
They took away the Fremen super unit, but let the Emperor keep his, because…reasons?
They took out blank cards. I can see wanting to remove that aspect in the game, but again they were a pretty big part of the balance (played into Harkonen and Atreidis strength) and they didn’t replace the part they removed with anything else.
There was something about with the way the card worked that triggered alliances that they changed that made it less turbulent, but I can’t recall it.
A new rule they put in was “no secret talking”, which was a huge nerf to Atredis since they relied on information brokering.
They took away all factions being able to trade money at the end of a turn, which was a HUGE boost the Emperor. The Hacan (Guild equivalent) in REX often have tons of money they can’t do anything with because they don’tneed it for movement, and they suck in combat due to their weak leaders.
WHY ARE YOU BOOSTING THE EMPEROR SO MUCH, FFG!!! He was already one of the strongest factions in Dune, requiring careful play by everyone to not hand him the game. Then they went and hobbled all his rivals. The emperor got major boosts, the Bene-Gessrit went untouched, and everyone else got indirectly nerfed when they removed or downplayed a bunch of mechanics that played into their strength but didn’t compensate for it. I…have no idea why they just straight up removed the Fremen super unit.
Dune took longer to play, but it was worth it.