I posted a table with the haste values needed for the 40% with each version of Thok's trinket somewhere in this thread. I will find it and relink it, I suppose.
- - - Updated - - -
Here is a small table to show the ilvls versus the actual % you get:
I will assume we have the VP needed to upgrade the items and do my math from there.
LFR(2/2): 5.9754% | 17000 / 1.059754 =
16041 Haste Rating
Flex(2/2): 6.6823% | 17000 / 1.066823 =
15935 Haste Rating
Normal(2/2): 7.5427% | 17000 / 1.075427 =
15808 Haste Rating
WF-Normal(2/2): 7.9764% | 17000 / 1.079764 =
15744 Haste Rating
Heroic(2/2): 8.514% | 17000 / 1.08514 =
15666 Haste Rating
WF-Heroic(2/2): 9.0035 | 17000 / 1.090035 =
15596 Haste Rating