Can you link or reproduce the builds?
I can probably do out some math that gives the pt for pt value of the talents, but I did the math for myself offline (trying to find a new home for my CE point, RIP Corpse Explosion), and I found that Sudden Doom is a better improvement in threat than Necrosis, point for point. I imagine Subversion would work out the same.
(I'm still using my 3.1 build with the 1 pt moved, since nothing else has really changed. I'll be posting something in the coming weeks discussing that, once I have a better feeling for how it all feels.)