(This entire post assumes Fire)
There is the list of the PPM adjustment changes. The Sinister Primal Diamond has a RPPM base of 1.18. Because of fire mage, that is multiplied by 0.302. Which gives us a RPPM of 0.35636 for fire.
Now we use the RPPM formula for determining how much of a stat you gain:
[[(PPM) * 1.25(Haste) * Duration of Trinket] / 60] * Stats granted on proc
Plugging the numbers in, assuming 30% haste = 12750 rating, we gain only 112 haste rating. (This assumes a base character haste rating of 11.8%, which is just my haste rating because I'm lazy.)
So to compare.
With the burning we have 216 int and 3% crit rating.
With the legendary meta we have 324 crit rating and 112 haste.
Am I the only one that sees the problem? How can something be legendary and not be an upgrade over the current basic gem we're using?