It wasn't so much that IEs get 1-shot end-game, it was that Melee Sorc was strong enough by that point that she didn't need summons anymore. Right now, I'll say Lightning/Cold is probably still the better end-game spec, but getting there will be harder.
The IE nerf affects a lot more than just Sorc tankiness. Part of the reason Frost Armor was so great was that it allowed for tanky summons without having to waste tons of hard points on them. This meant you could focus on building your Sorc instead of boosting summons. It also allowed for a wider variety of mercs, making Rogue Priestess one of the best mercs for a Sorc because of how well IE aura+Vindicate synergized with one another (a properly-built Priestess could do D-Fauzt with only Sorc summons to tank). Without Frost Armor, it throws the viability of that into question.
As Hecht said, it's not much of a buff. You're losing 150% TCD aura, getting weaker+more expensive Blade Spirits, a weaker merc, and fewer meatshields overall. And all you're gaining is an extra 5% DR.
I 100% agree that the other buffs dont make up for the Cold nerf, I guess my question is more of how the other elemental tree's defensive passives compared with the nerfed version of the Cold tree. I dont have a great understanding of how valuable Maximum health vs Defense vs damage resistence actually is. edit: though I agree the Living flame regen is definitely pointless when sorc has Symbol of Esu
Without the TCD aura, putting points into Ice elementals will still buff your Blade Spirits, and you also get the minion damage aura. But if you now need to invest more into boosting summons, that kinda sucks.