Greetings,

As you're linking to an Arena reward, I guess you intend to use your priest(s) for PvP with a Disc/Holy or Disc/Shadow build.

Unbreakable Will 5/5 should come first then, 15% resist to stun-fear-silence is key to survive.
Wand DPS only useful IF you survive, and you may not have any talent points available for both tier 1 talents at 5/5.

PvE wise might different, though if you play on a PvP server UnWill gets my preference without a doubt.

/salute