Dhokmak does not use normal melee auto attack rounds. Instead, he uses a TP attack every 3~5 seconds if his current target is in range that consumes all shadows. If his current target is not in range, he uses a ranged attack every 3~5 seconds that inflicts a weak poison on the target (<50 HP/tic) and ignores shadows.
Fetid Eddies: AoE Gravity and knockback
Nullifying Rain: AoE or conal mass Dispel (3~5 buffs) and damage
Noyade: Conal Silence and places a stationary pool of poison on the target (300+ HP per tick while in the pool)
Cesspool: AoE HP Down
Since Dhokmak is extremely susceptible to gravity and does not appear to build resistance, a viable strategy is to kite him around the room and nuke him with thunder magic.