The beta was undoubtedly much harder than live, relatively speaking. On live, permadeath means you can never wipe to learn an encounter or understand a boss's ability. If the game was as easy in beta as it was on live, presumably everyone would have had a huge advantage due to the lack of permadeath.
I'm purely talking about encounter difficulty in a design sense. Obviously the reason no one cleared Floor 1 is because they expected to be rescued, were refusing to participate, were playing SUPER cautiously so as not to die, etc, not because it was made harder from a design perspective. The change to the first boss didn't even make it harder, it just made it different from what they were expecting.