Yes.
1 (base shadow word: pain damage) * 1.25 (25% sw: Pain buff) * 1.0417 (Shadowform buff, 1.25/1.20) = 1.3021
So, 5.2 buffed Shadow Word: Pain by 30.21% from the damage it did in 5.0/5.1.
This hotfix did this:
1.3021 * 0.75 (-25% shadow word: pain nerf) = 0.9766
So after this nerf, despite the 5% Shadowform buff, Shadow Word: Pain now does 97.66% of the damage it did in 5.0/5.1. To phrase it another way, it lost -25% compared to Live, and lost -2.34% compared to 5.0/5.1.
It's a massive nerf compared to live, a small nerf compared to 5.0/5.1 - but the reason people are annoyed by this is that we were meant to be getting buffed this patch, not small-nerfed.
As sad as it is, I can't even bring myself to look at it, because a couple lines up - they buffed all mage bombs by +40% O.O
Mages are still the top DPS specs in PvE, Frost is bizarrely the top single target spec in the game right now in PvE. A 40% buff to their biggest burst ability means I probably can't even zone into bgs/arenas/rbgs this season, which is depressing - I was actually thinking things might get better on the PvP front.
For those curious on current PvE Patchwerk standings (pre-mage buffs and spriest nerfs):
http://simulationcraft.org/520/Raid_T14H.html
After the Shadow Word: Pain nerf, my napkin math says we're easily last place again (@ 117,058 DPS).