Is there? There is ample evidence for Warriors/NR in general being overpowered, indicated by their abnormally high winrate across all ranks.And saying "it's good enough, just get better" where there's ample evidence it doesn't perform well compared to other factions even for the best players
There's no definitive proof for NG/SY being bad in general, though. Try not looking at clearly overpowered decks at the top for a second.
Now you see that NG and SY leaders generally have same distribution of high/low winrates as everyone else.
The whole hassle is a byproduct of some new broken shit introduced to the game, not excessive nerfs.