I too felt that even lightning build will not be endgame. So far Holy build is only one I saw on twitch.tv that is end game viable.
If you want to see. You can search Mannercookie in twitch.tv/youtube.
This morning he was timing his 10 T6 run (Without Unity on follower). Try to goes as fast as he can and try to beat OP Witch Doctor that can clear in 8 mins or so. . He cleared them Average around 10 to 13 mins per run.

He did try to swap some skills and gears to optimized the time. But his key pieces are BOP, 5 pcs Akkhan with Ring of royal granduer, 2 pcs born set. His CDR is around 45%

I am damn lucky to get this SOJ. Perfect roll on Holy dmg and Elite bonus. Too bad I still can get 8% CDR on it.

For solo, I normally swap out and use Unity. Put another unity at follower and easy mode up to T5.