Engulf needs a buff or a change of mechanic. It's a tier 6 mage talent, yet most people agree that it's redundant. Engulf is an AoE bleed that doesn't damage the enemy it's casted on. Its purpose is an AoE DoT, but it isnt viable as it has a 2 second cast time and over 10 seconds only does 300% spell dps. There are more effective AoEs that make engulf redundant. I believe the cast time is fine, as it's an upper tier spell and I like the animation. Its effect could use a rework.
Some suggestions to make engulf more useful as a tier 6 talent would be:
1. Engulf can act as a self-buff that reduces the cooldown or increases the damage of fire spells.
2. Engulf can be applied to allies like tanks so it acts like a buff. It may also increase armor or spell defense/dodge based on caster's spell power.
3. Engulf can be a casted AoE explosion. One very large flame donut that does damage in a huge radius at the target location. The damage can be instantaneous or inflict DoT burn.
4. Engulf can propagate across multiple enemies and damage is instantaneous. i.e. Flame donuts can spread.