To fully prepare yourself for the Expansion Reaper of Souls and Paragon 2.0, you have only one thing to do that is to power level your heroes to Paragon Level 100 as more as possible. Among the five classes, only Barbarian with WW/ Rend Skorn build is the most efficient one. What's more, it is the class can be build for Monster Power 10 cheap and easily. If you have 25 million Diablo 3 Gold in account, then we can start now.

This is the video my Barbarian works:

Diablo 3 WW Rend Build - http://us.battle.net/d3/en/calculator/barbarian#chQRUP!YZg!aZZYZc

Rend- Rarage: rune to increase range
Whirlwind - Hurricane: rune to move at Sprint bonus speed
Overpower - Klling Spree: critical hit chance increase 10%
Battle Rage - Into the Fray: CC generate Fury
Sprint - Run Like Wind: Tornadoes killing
Wrath of the Berserker - Thrive on Chaos

Passive Skills: Weapons Master, Ruthless, Brawler

As long as there is high monster density, you do not need to worry about the Fury generation issue. Just like the Wizard Archon build in Decaying Crypt. You can do as your heart please. With five pieces of Immortal King set which would give you 4 Fury per second, you can change the passive skill to Unforgiving to full Fury and then change back. If your all resistance and armor not meet the MP10 requirements, you can change Overpower to Warcry. But I would not suggest you to do so. To take full advantage of Brawler, you should learn to draw all the monster together and Rend WW.

One tip for you in the Auction House: search for life% and low Vitality instead of high vitality. This always give you a good bargain instead. Or at least, it gives you more choices.

Items to Craft: Bracers, Shoulders, Amulets. To meet the EHP, you can craft Vitality Shoulders.

Gear Requirements:
45K EHP
500 all resistance
58k armor
10% melee reduction

Weapon: Skorn with Lifesteal. Although you would have life steal in the Immortal King belt, it is not enough in high MP. Lifesteal in weapon can increase your survival rate with the passive skill Brawler as well. To have enough life recovery, your DPS should not below with 100k unbuffed.

Areas to Farm:
Act I: Festering Woods - (Leorics Manor) - Fields of Misery - Halls of Agony - The Weeping Hollow

For Decaying Cryp runs, you can go to http://www.salediablo3.com/news/index-373-diablo-3-guide-decaying-crypt-location-and-farming

Act II: Sewers of Caldeum + Black Canyon Mines + Road to Alcarnus to get five NV - Dahlgur Oasis if you find Forgotten Ruins, you can get into as well.