Rag seems way stronger to me this time round. His minions are still bonkers, and Nefarian definitely feels like he's been nerfed.
I mean if Nefarian gets a good spell or two from his HP, sure, but that doesn't actually happen that often. I more often get Arcane missiles and such crud than anything actually useful; and Nefarians minions are severely average.
I lost a game the other day by drawing no minions as Nefarian for 6 turns or something, just drawing spells like useless shadowflames and HPing for spells, and 3 of the spells that came from the Hero Power were Ancestor's Call, which is obviously actively harmful when you have no minions.
The 8 mana whelp thing that Nefarian has is the biggest powerhouse it seems to me, mostly just because it draws the inevitable flamestrike so you can actually play midsize minions fairly safely. Anything big you play as Nefarian in the late game just gets Ragsniped, you have to rely on flooding the board a couple times until it manages not to get wiped for once.