So before this patch, I found out that if you logout in a major city with Spirit of Redemption you relog with full health and mana. Now in 5.0.4 they released a glyph that increases your Spirit of Redemption duration by 10 seconds, so if you die anywhere, you have enough time for a 20 second logout.
Steps:
1: Get the glyph Glyph of Spirit of Redemption - Spell - World of Warcraft
2: Once you gain Spirit form, logout asap.
3: Relog, full health and mana.. Profit.
I'm making a video on me doing this in Battlegrounds and it will be out shortly!