This is the build I've been using in Hero Battles and other PvP for about 2 weeks, it absolutely ruins everyone. Use it fast though, I predict a bit hit from the nerfbat this afternoon:

Wounding Strike [E]
Mystic Sweep
Chilling Sweep
Signet Of Mystic Speed
Heart Of Fury
Conjure Lightning
Attacker's Insight
Faithful Intervention

Scythe Mastery: 12+1+1
Wind Prayers: 8+1
Mysticism: 8+1
Air Magic: 7