Downstairs does seems more health than before, but I can't tell you how much more since I've always sent "too many" downstairs for the first 40/20% (final 20% we only ever sent two but we never made it that far last night) just to get in and out quick and then clean up adds up top after. The very first attempt we did blow up downstairs a percent short, but part of that was that multiple people I assigned to go down didn't. I added a few more people later, probably too many in theory but banking on the fact that some people wouldn't actually go (and they didn't), and it was fine.
We had a harder time dealing with the Fated affix itself on that fight shielding things at the worst time and not getting the shield down fast enough (or the adds down fast enough after getting the shield down). In a fight that is already "everything needs to die first/fast," adding a barrier to the mix seemed unideal. Starting in the second round, we lost people to attrition, and then dealing with shelded MCs, shielded tank adds, shielded little skeletons, shielded icicles, shielded aboms, etc, in the later phases sucked. I think a lot of it was just the chaos of the fight. People complained they couldn't find the barrier fast enough in a sea of skeletons and with such a melee heavy group it was quick a lot of running around to the current priority target rather than DPSing. But some of it was also just really unfortunate timing, like adding the barrier to icicles gives you so little time to dps them to space out their health (with the barrier chunking a lot of it it immediately), or losing a tank because of how the shield overlapped with the tank adds or aboms (or both), etc. We wiped four times on the fight and then ran out of time. We'll finish up Thursday.
That said, part of it is probably my fault for just throwing everyone into it expecting it to fall over like all the prior Fated bosses (we one shot everything in Nathria minus one bugged abiliity, and everything prior in Sanctum), even with several that didn't know/remember the fight and at least one hard carry. It's not a very good fight for people to just wing. I'll go into it Thursday with a little bit more of a plan and clearer instructions so hopefully it's less of a mess.
Edit: one shot it the second night (very clean/smooth one shot) with people paying more attention. It does help to prematurely dispel the barrier add out before tank adds or icicles go out so it doesn't fall off naturally and shield them all, so I recommend doing that.