When spirit got buffed, the za neck became the best neck for holy priests ingame. Thus, I don't know why the neck from felmyst got a very high item level.
It got high level because Blizzard's math team decided it's an appropriate level for that item In this case, I assume they thought that 33 stamina on Brooch of the Highborne is worth a lot. More about how Blizz decides item level can be found here: http://www.wowwiki.com/Item_level
In this case, I assume they thought that 33 stamina on Brooch of the Highborne is worth a lot.