These are very dependent on what gear you have as sometimes your stat weights might be different; I would advise using raidbots to check what is best for the gear you have.
Mastery always pulls ahead with the more targets in the encounter, you generally want to try to have a nice balance of haste/mastery. Haste helps with shard regeneration and is generally better with ST situations.
Haste makes your cast spells quicker and reduces the cooldown of your Conflagrate. It also increases the tick rate of your Immolate. Pets also scale better the more haste you have. This is why haste is such a valued stat.
Mastery is a passive damage effect through Chaotic Energies which increases your damage dealt by a random amount.
Critical Strike increases the chances that your spells and abilities will hit with a critical hit. Your Chaos Bolt hits harder with the more critical strike you have because it always crits. So essentially it increases its damage by 1% with every 1% of critical strike you have. Pets yet again scale with critical strike and so does your Immolate which can increase shard regeneration.
Versatility is just a damage done increase and damage taken reduction.
The best way to calculate stat priorities for your character is to "sim" your characterFind out how to sim
The best race for warlock is always Troll - Having an extra CD which increases your haste during burst windows on progression is always the best.
For the general player you will want to Enchant your gear with;
Always use raidbots to see what stat is best for you though.
Mastery: Masterful Jewel Cluster
Flask: Spectral Flask of Power
Potions: Potion of Spectral Intellect
Health Potions: Spiritual Healing Potion