A#2: You also need to include the +20 int gems that you would have to give up in order to activate the meta.
Meta + gems to activate = Meta + gems to activate
Insightful + 2 King's Amber + Nightmare Tear = Ember + 2 Luminous Ametrine + Nightmare Tear
Subtract out the Nightmare Tears and add values to each of the gems:
21 int + ~70mp5 + 40 int = 25SP + 2% int increase + 24SP + 20 int
Gather like terms together:
61 int + 70 mp5 = 49SP + 20 int + 2% int increase
Simplifying terms:
41 int + 70 mp5 = 49SP + 2% int increase
Now, let's ignore the SP gains as they're kind of irrelevant to our needs. At what point would the 2% int increase outweigh 41 int and 70 mp5. For myself, if I could gain 100 intellect, I would change metas. Let's do the math to figure out how high your intellect needs to be in order for that to happen. Intellect is affected by three buffs: kings (+10%), Mark of the Wild (+52 int talented) and Arcane Intellect (+ 60 int). It is also affected by our Divine Intellect to give us another 10% multiplier. Therefore, our 2% increase would be .02*((Base Intellect + 54 + 60) * 1.1 )* 1.1.
.02* ((Base Int + 114) * 1.1 * 1.1) = 141 int
Base int + 114 = 5826 int
Base int required for the meta to give 2% gain of 100 intellect = 5712
We will not see this amount of intellect on our gear in this expansion. It's a poor choice in metas.