Mistweavers were not nerfed.
Renewing Mists jumps one less time, yes, but it tics 50% faster.
The haste bonus on Stance of the Wise Serpent does not exist on live. Chances are 150% was a typo from a previous beta build. That's still a buff, either way. It doesn't exist on live, so when it hits live, MWs get 50% more haste from their gear.
Their mana costs were bumped up a bit, but not enough to matter.
And Healing Spheres... no one used them anyway.