I was trying to understand what blizz was thinking for doing the changes they did and I think I got it.
Problem “almost every build focus around vulnerable and crit”
Objective “Have builds to use different stats beside crit and vulnerable”
Solution “Nerf vulnerable and crit”
Imo, what they should have done is calculate the max value you can get from vulnerable dmg from all sources, like rings, paragon boards, etc. Lets say you can get from all that 500% vuln dmg just to say a number. Now do the same with crit and all other stats (like dmg to slow, dmg to frozen, dmg with barrier, dmg with shadow, etc). Make them all have the same final possible % dmg amount (all of them to have 500% max dmg to keep with the same number from the example).
However, after that, the problem is not fixed because you cant apply slow or freeze to bosses for example, so make a glyph that have a passive that says “crowd control dmg multipliers apply to all enemies, even to bosses”. That way building around every single stat is now perfectly viable and now I can choose other stats beside vulnerable and crit.
Finally, remove almost every changes they did in the patch. Take half a season or a full season to test and have data and, in season 2, make nerfs if needed.