especially for a melee character

So, 4 KWs and 4 keys. You need one of each key to make each new of the 4 new Infernal Machine recipes, and each of those opens one new portal. There are now 4 portals, one new level with a new Uber(s),

wow items

 and each of the Portals can provide you with 1 new Demonic Organ. (Those are also dropping at 100% for now.) The Hellfire Rings are also new. They grant +45% EXP now, roll with bigger Loot 2.0-sized stats, and the special proc effect is a sort of fire nova explosion that’s actually pretty useful,

d3 items

 especially for a melee character.
Click through for lots of screens of the new stuff, including some completed rings, the new Portal and Uber level, and other related stuff. There’s even a video showing the whole process.