Fire Mage gearing help

[darkxiao]

Moderator note: moved to Q&A.

Hello all, I was wondering if any of you could give me a bit of insight on how I should be gearing my fire mage. Here is my character:
https://worldofwarcraft.com/en-us/ch.. ... et="_blank

Lately, I've been hearing people talk about the NH 2-pc and how I should pair it with the ToS 4-pc, and I've also been hearing people talk about equipping the highest level pieces instead and not to worry about the NH 2-pc. Apparently, this is more beneficial to frost than fire for the NH 2-pc. Is this true? Also, I'm confused in how much crit stacking I should be doing compared to other stats. I use raidbots and pawn to equip gear based on my stat weights, but I'm still confused in how much % of crit or any of the other stats I should have. If anyone can give me a bit more insight into this would be great! Thank you for your time!