TYPO ON TITLE, THESE ARE STAT PRIORITIES. THERE AREN'T ANY WEIGHTS.
Stats are finally done. This was worked on with Aughyssul who writes for Icy-Veins/Wowhead. The reasoning for the stats are as follows.
Versatility: Due to the higher amount of magic damage, and our lower resistance to it, Vers will help bridge this gap. It also works to increase our heals and dps throughput. Do not panic though, there are only 2 pieces in Nighthold with Vers on it, so you may enchant Vers, but don't expect to have it on more than a few pieces.
Haste: Lowers GCD, Lowers CDS on: Immolation Aura / Demon Spikes / Felblade. This helps with having abilities up more often for more pain generation and frequency that you can cast AM and heals.
Mastery: Increases Attack Power which increases Damage and Healing. Also increases our Physical Resistance during Demon Spikes.
Crit: Chance for higher damage and healing. Gives parry at roughly 1/3 of the value of your crit %.
A note for Legion.
Due to pain from damage taken, Haste and Mastery may flip flop due to your skill/gear/encounter. If you have a higher damage taken, then Mastery should help more, as you are gaining so much pain that you can Soul Cleave and Haste becomes more and more useless. On the contrary, if you have less damage taken, Haste will help make up for some of the Pain, allowing things to go smoother with higher AM uptime.
So what are the stat weights?
IN LEGION
Survival: Vers > Haste > Mastery > Crit
DPS: Mastery = Crit >= Vers >= Haste
In Mythic+ Dungeons: Mastery > Crit >= Vers > Haste