Seeing as the 4th war was pretty much instigated by Sylvanas to funnel souls to the maw ( Even though some horde players like me felt it was justified before what everyone said about her was right and she pissed off ).
She made the pact with the jailer after Arthas died, so nuking Gilneas was for the jailer, then more bad stuff, then Lordaeron, Teldrassil, The war at large, Sylvanas being absent from battle for dazar'alor, and helping to free N'zoth. But all this at large, must just be a drop in the Ocean compared to the rest of the universe? Billions of worlds, billions of wars, billions of deaths. Then you have Teldrassil that was just maybe a hundred thousand?
I don't think it would have made a difference