Haste increases attack and spell casting speed, adds additional damage and healing to DoTs and HoTs, and reduces the GCD.

Mastery provides a passive bonus to your character based on your specialization. Mastery Potent Afflictions increases the damage done by your DoTs like Agony, Corruption, and Unstable Affliction.

Intellect increases the damage and healing done by your spells.

Versatility increases your damage, healing, and absorption done and decreases damage received.

Critical Strike increase the chance for your spells and attacks to critically hit for additional damage and healing.