Mouse Skills:Firebomb (Fire Pit)
Spirit Barrage (Phantasm)
Hotbar Skills:Grasp of the Dead (Desperate Grasp)
Acid Cloud (Slow Burn)
Wall of Zombies (Unrelenting)
Big Bad Voodoo (Boogie Man) OR Locust Swarm (Diseased Swarm)
Passive Skills:Vision Quest
Pierce the Veil OR Gruesome Feast OR Grave Injustice
Blood Ritual OR Spiritual Attunement
Fire Pit and Phantasm are your most frequently used skills here- they lack the cooldowns of your non-poison hotbar skills, the high cost of Acid Cloud, and the unstackability of Locust Swarm. While these skills do lay down damaging zones, those zones are relatively small and don’t last very long, so keep firing in the path of your main target when using those. Grasp of the Dead is your opening shot in all fights, keeping things slowed and restricted so that you can keep them in multiple zones at once. If you’re using Locust Swarm, that makes a good followup before firing your actual zones- Big Bad Voodoo is more useful if you’re in a party, and should be avoided if you don’t party much.
Acid Cloud is your biggest source of damage, not just for duration and area, but in terms of total damage per use. This makes it your ‘main cannon’, so to speak, so it should come out before you switch over to Phantasm and Fire Pit. Slow Burn makes it last a long time, so you shouldn’t need to use it too many times. If Grasp of the Dead isn’t doing enough- either because enemies are jumping on you right through it, or because your foes flee the funny-colored ground, then you can use Wall of Zombies to restrict their movement towards or away from you. Wall of Zombies has a fairly large cooldown, though, so don’t try to rely on it for consistent damage.
Vision Quest and Blood Ritual are effective ways to boost your Mana, though Blood Ritual does so at the expense of your Health. Ideally this won’t be an issue, because you’ll be keeping things staggered and thus away from you. If this isn’t cutting it and you find yourself faceplanting too often, then you can switch it out for Spiritual Attunement, which is not as effective but much less dangerous. Pierce the Veil lets you take advantage of your increased Mana resource, letting you spend more for stronger damage. If you run dry of Mana often and don’t have any damage woes at all, you can probably swap this out for Gruesome Feast to not only cut your Mana costs but give you a decent shot at regular Mana recharges, or for Grave Injustice to draw a steady benefit off the enemies that manage to get near you, only to die before they can actually swing a fist or weapon.