it really depends on your skill level as nearly all builds including LoN LTK can hit GR70 easy.
You can easily get it with Multishot DH assuming you know how to stutter step properly.
The easy builds that can get it:
Helltooth Garg WD
LoN Bomb sader
Charge barb (both versions)
You also need to remember Blizzard is nerfing the one mob type that is stronger than elites. Moon clan impalers. For the most part the goat men are what kills people in GRs aside from lag.