Gratz on the legendary neck! Sure there are more fancy resto shaman specific legendaries to get, but the neck is far from bad, so enjoy!
In terms of enchants, there’s the enchant that randomly procs a heal and passes through the raid (priestess if I’m not mistaken). So far that one has been underwhelming in performance. Second preference goes out to the neck enchant that gives flatout 300 mastery. Alternatives in the future and for other classes is the flat stat crit/haste combo another enchant offers. So far, I’m running mastery though.