After having spent over a dozen hours on season 5, I just hit 70 this weekend and got the full tier set (Shadow's to be precise). The only two things I have left to do is equip a level 70 legendary in every slot (which I've done, and yet no achieve... does it discriminate against set pieces?) and complete a set dungeon. I just spent half an hour attempting to complete the latter and failed; the skeletons with shields and the elite mobs apparently break your chain meaning you have to skip them entirely and continue looking for necromancers and normal skeletons, which takes quite simply far too much time to complete. (If you hurl an imaple at a skeleton with a shield, they block the attack and since that didn't count as a "hit" your streak breaks. The elite mobs survive the impale and for some reason that breaks the streak despite being hit, so apparently every single impale MUST kill something for it to count). Yes, I followed the guides and have tried out several different setups.
My toon: http://us.battle.net/d3/en/profile/V.../hero/54317047
(Note that I took off the Wreath Lightning gem and the belt before I went into the dungeon, in case they'd break the chain with their passive damage).