EDIT 2017-1-18: Check out the 7.1.5 Gear Spreadsheets for Nighthold.
As I discussed in my prior post about Preparing for The Emerald Nightmare, it can be useful, after you have done all your other prep, to figure out what gear you should be targeting in the instance.
For reference, here is my gear as of last night.
I created a spreadsheet, outlining the possible upgrades in the Emerald Nightmare for my class and spec. If you are a Balance Druid that wants to use this sheet, I urge you to make a copy and enter your own starting gear, as well as to continue to update stat weights using a source you trust.
This sort of spreadsheet has limited usefulness, as there are many out-of-raid sources of gear in Legion and titanforging exists. This sheet serves the limited purpose of showing what upgrades exist for me, from the raid.
If you play any other class, this spreadsheet may serve as a model of something you want to create for yourself.
One insight demonstrated by spreadsheet that is applicable to Balance Druids and may be of use to other classes: the crafted ring and neck-piece are better than non-warforged/non-socketed rings and neck-pieces available from the mythic raid.
Balance Druids should look into getting these pieces if possible. Other classes should research them, especially if your class has a secondary stat that is valued much more highly than the other secondary stats.