Went to test it on the PTR, since the there's nothing to suggest this fight will be made any harder come next patch. Quite the opposite is possible with the GC change. Sadly I need to do normal mode first on PTR due to the copying system. Might do it next week, but I don't really see the fuss.
Depending on whether or not the nerfs were done on a mechanics or coding level, the lose of Defile and Remoreless winter will hurt quite a bit. The adds will cost maybe 50k vengeance all up, a hefty loss but will be supplemented by additional GC procs. The base ilevel may be pushed up a bit without defile/rw, but with the catch up systems and such in place, I don't see that as a point of worry either.
All in all, rather than spending your time graphing estimations and preaching doom, it might be better off either testing it on PTR or just kicking back and not worrying about it.