Nerfs definitely make sense, but they missed a ton of ridiculously overpowered legendaries. For example:
http://www.wowhead.com/item=137060/archavons-heavy-hand
This one reduces the cost of Arms' primary damaging ability by a whopping 75%. Insanely powerful. Wasn't nerfed.
http://www.wowhead.com/item=137072/amanthuls-wisdom
This one allows a resto druid to pre-HoT ~10 people while drastically reducing overhealing! Game-changing for raid healing. Not nerfed either.
http://www.wowhead.com/item=132451/m...he-rune-master
This one rewards Arcane 16% of its maximum mana when casting Arcane Barrage. Burning then conserving mana is core to Arcane gameplay, so this is just incredibly powerful too.
So while they may be nerfing a few outliers that were even more powerful than these three (and many others, I picked them at random), it is not correct to say that legendaries are "a nice bonus" now. They're still absolutely one hundred percent mandatory.