The proc chance is insanely low; something like .01% according to the math given in the initial explanation of RPPM.
As I mentioned, on live I have 3036 Haste, which is something like 12.6% with the 5% raid buff. Going with the 1.4 seconds since the last chance to proc that's given in the description (It will often be less than a second since last chance to proc due to DoT ticks and ToC having the short GCD) we have a equation of: 0.5(ppm) * 1.126(haste) * 1.4(time since last chance) / 60 = 0.013136% chance for a proc. More often than not, the chance will be even lower than that. Our initial cast has the 10 second time since last chance, giving a 0.09383% chance for a proc...Originally Posted by 68927995382
That considered, massive dry spells will happen frequently. Personally, I'll be looking at other trinkets as I expect their values to increase dramatically when given the same treatment in Simcraft that Zinnin gave this trinket.
Also, I edited the default APL specifically for the Unnering Vision of Lei Shen, so it is going to be higher on this list then it might be in practice.