I've been playing around with builds for a bit and have been running this since level 51. I find it to be fairly enjoyable and easier on the hands since I don't spam buttons as hard due to cast timers. I welcome any feedback.

Starting at 51 with 16-51-0
http://rift.magelo.com/en/soultree#UkdFww/nkll4Faaiog/r
I'm currently level 54 with 19-51-0
http://rift.magelo.com/en/soultree#UkfFz4/nkll4Faaiog/r
Eventually leading to
http://rift.magelo.com/en/soultree#UkaAAS/nkll4Faaiog/r

The last soul can be Purifier if you want to toss a shield on your beacon, Cabalist for extra AoE or Justicar for a small steady heal.

Buffs:
Armor of Treachery / Armor of Awakening
Shroud of Agony
Spiritual Protection
Rage Blight

I have two macros:
1. Sanction
#show Sanction Heretic
suppressmacrofailures
cast @mouseover Marrow Harvest
cast @mouseover Sanction Heretic
cast @mouseover Vex

2. AoE*
#show Soul Drain
suppressmacrofailures
cast Soul Drain
cast @mouseover Circle of Oblivion

*Add "cast Bound Fate" above Soul Drain if using Cabalist.

How to play:

Single target

Place the Beacon of Despair at your feet (not your target's). Then hit the Sanction macro to cast Marrow Harvest followed by Bolt of Depravity and then spam Sanction macro twice to cast Sanction Heretic and Vex. Finish by casting Siphon Vitality. By now the target is attacking your beacon.

Use Husk of Indifference if your taking a lot of damage. Use Bolt of Depravity when it pops up for instant cast but otherwise stick to Retribution. Keep Marrow Harvest up and use Sanction Heretic as it cools. Refresh Siphon Vitality from time to time.

Difficult mobs you might toss Spiritual Deficiency on and hit it with Nysyr's Rebuke which does a great deal of damage. Additionally you can place the beacon away from you so that the mob will run towards you but at the last moment turn and head toward the beacon since it seems to only work at about 20m. Let's you kite a bit before you start taking damage.

Use Foul Growth / Loathsome Restoration as needed on yourself or Beacon.


AoE

I can typically handle 3-4 equal level mobs as long as I keep an eye on my beacon's health and pull intelligently. When it gets to be too low I use Trepidation and fear the mobs away while I heal up.

Other than keeping Siphon refreshed on all targets I spam the AoE macro to alternate Soul Drain and Circle of Oblivion. If a caster refuses to come close I hit it with Nysyr's Rebuke to get rid of it.

Mana concerns are non-existent. This build seems to have near infinite mana.

DPS
Single target using quest gear or Nysyr's at level 54 I bounce between 2700 dps and 3100 dps.

AOE I tend to sit around 4000ish. Depends on the situation and number of mobs.