So just to quickly compare pre and post changes, I usually run Leviathan HTB (which was not adjusted) as BLU/RUN + GEO/WHM to gauge the impact of vex and attunement changes (Idris, 900 skill, no BoGs)
Edit: moved conclusion to top
Conclusion/TLDR: It is not possible to reach the same potency of previous vex, by combining new effects vex and attune with +50 m.eva from food. Bring a WHM and/or Carols on top of Vex
Pre-update, I would get the occasional un-resisted hit from magic BPS/ Waterja, but very occasional, and very very rarely full damage hits using indi-vex, sulporX2, vallation, /whm barwatera with legs (total 159 water resist) with mixed -DT gear (316 m.eva in gear)
I tried 3 varieties of 7 runs, the first using the exact same setup as pre-update. Unfortunately I was unable to complete the first kill as unresisted damage from additional effects + a hit from grand fall or waterja would spell my doom immediately. I adjusted a bit adding barrier tusk and zephyr mantle for added defensive abilities and finished the rest with several close calls of sub 100 hp. 3 out of 7 runs ended in failure. One before even dealing 10% to a unresisted, unabsorbed double attack / added effect of 700+
The second set I tried going 7 runs using indi-vex and geo-attunement. The resists were a little better but honestly not much compared to my first set. The addition of attunement was not enough to greatly mitigate incoming damage but there were less full hits, and 1/4 resists were more common. The same issues arose as previous. Spamming cures became an issue for MP, at least on the GEO's part. 1 out of 7 runs ended in failure.
The third set I ran went with using Miso Ramen as food for an extra 50 m.eva to gauge the incremental impact, while still using both vex and attune. On this set, less then half of spells and magical blood pacts landed for full damage, most common being 1/4 resists. This was much more manageable but there remains very close calls, surely death if HP wasn't kept at maximum at all times.
In all cases, one major difference I must point out is that trusts can no longer survive at all vs the incomming magical damage compared to before. This makes it much more difficult for those planning to keep soloing / low man, so please take care.
These changes I think are quite beneficial into pushing the inclusion of whm (the trusts to shellra V sure, but die not long after) for the merited bonus to shellra V, along with a proper barwatera set to reach 300+ resist rates along with making things that should be more "difficult" a bit more group focused.