From the looks of uncategorized spells and Celestial related legendary quest chain, it seems like the procs themselves are related to the four Celestials and their areas of expertise.
Tanks: Endurance of Niuzao
Physical Dps: Flurry of Xuen (melee dps/hunters)
Caster Dps: Essence of Yu'lon
Healers: Spirit of Chi-Ji
As with everything on PTR, this is pure speculation and can change at a moment's notice.
(moved from General)