I was looking for a build that would kill very fast, have good mana support, and be able to deal equally with huge mobs and bosses.
For monster groups the build works as follows:
Hit group with Locust Swarm (for mana generation to support bears), wait one second for the Swarm to start multiplying, hit Soul Harvest (for DPS and LS boost), throw bears until monsters are dead or OoM. Then throw spirit barrage to clean up stragglers and to get mana regen going again.
Use SW, and Soul Harvest as needed to keep the mob from stun locking you.
For elite packs/bosses the build works as follows:
Lead off with WoS, keep it up until they close on you, use SW or Horrify as the situation warrants(use in rotation - these skills keep you alive), throw SH on them when they close on you, bear them/WoS them depending on range. Keep SW and Horrify up in rotation throughout the fight. Rinse and repeat until they are dead.
BR - To reduce spell mana cost
RoE - Enables WoS spam. With the Zuni set you should be able to spam WoS with RoE indefinitely. This is your go to ranged spell, straggler spell, fast mover spell, and boss killer spell.
JF, SV, or GF - Try all three and see which you like best. GF if you are more tanky. I recommend most people use SV for the skill synergies as discussed below.
Rush of Essence (RoE) - Spirit spells return 40 mana over 10 seconds. For my skills shown above I'm using 4 spirit spells: WoS, SW, SH, and Horrify. Plus you can spam WoS when low on mana if you have the zuni set and not too much attack speed.
Spirit Vessel - Not only a save your bacon spell, but it reduces cool down by 2 seconds for SH, Horrify, and SW -- which is a very nice thing.
Obviously Locust Swarm will not help you much in a boss fight. So I recommend you use Haunt or Mass Confusion instead -- both are spirit spells and return mana from RoE. You can also use Hex, which is not a spirit spell, but it regens very fast and is a great boss spell.
Substituting Plague Bats or Cloud of Bats for Bears
Either skill can be substituted for bears. I am currently running the build with Plague Bats. And since PB has fewer mana requirements than bears, I use Hex (for bosses) instead of Locusts.