I found this while reading the new PTR Patchnotes:

PvP

  • Arenas
    • Bloodlust, Heroism, Time Warp and Ancient Hysteria can no longer be cast while in Arenas.




Source: http://blue.mmo-champion.com/topic/1...06-patch-notes

I don't know if this is a clear statement to role DK's for arena or to just "balance" arena. For me it is the kill for shaman teams.