1. Use Spiritwalker's Grace.
2. Start casting Ancestral Spirit while in LOS of your corpse
3. Run out of LOS from your enemy's and the corpse, just kite them arround so they can't hit you.
4. Run in LOS of your corpse again just before the cast ends.
This has helped me to pull off quite some resses in arena.
This might not be called an exploit, but I thought it was worth posting anyway since it gave me a couple of arena wins.