[Item] Tarnished sentinel medallion vs elemental shaman

[neuronul]

WoW Freakz item link: https://www.wow-freakz.com/item_finder.php?item=147017&&&&name=tarnished-sentinel-medallion
Bug description: In my previous post ( https://forum.wow-freakz.com/view-post-5898578.html ) I mistook spectral blast for spectral bolt and thus the post got rejected. In this post I would like to correct that.
In the proof linked bellow I've tried to test the spectral blast part of the trinket again in 2 different cases. What I tried to do is to mimic 2 player's playstyles and builds in order to achieve similar results for the number of times the trinket hits and the total damage of spectral blast. The players were chosen from the top 10 ladder on mythic goroth on retail.

Test 1:
Reference build and stats: https://www.warcraftlogs.com/reports/8HWcYdAQ2yqJ7mpC#fight=4&&type=summary&&source=5 (standard ascendance + elemental blast build)
The total damage done is somewhere between 250 and 300m with only 2 uses of the trinket ( https://www.warcraftlogs.com/reports/8HWcYdAQ2yqJ7mpC#fight=4&&type=damage-done&&source=5&&ability=246442 ) with BL and standard dps rotation.
Their number of hits and total damage is more than double of mine at almost the same stats and ilvl (see pictures 1 and 2 in proof section).

Test 2:
Reference build and stats: https://www.warcraftlogs.com/reports/bZA7qKQGHM9m6Php#fight=5&&type=summary&&source=1
The total damage done is somewhere between 250 and 300m with only 2 uses of the trinket ( https://www.warcraftlogs.com/reports/bZA7qKQGHM9m6Php#fight=5&&type=damage-done&&source=1&&ability=246442 ) with BL and with a rotation and build more oriented on haste and multiple uses of earth shock. This means that during the period in which the trinket is active the shaman can hit more spells than in the first build I've shown.
The result is the same as in the first test (see picture 3 in proof section).

I have two hypotheses:
1) The proc rate of the spectral blast part of the trinket is too low.
2) The trinket does not proc from shaman's overload (mastery). The text on the medallion says that it has a chance to cast a spectral bolt when the player casts something and shaman's mastery says that there is a chance that your spells get an extra cast.

Proof: https://imgur.com/a/qIIxCSe

[Barnacle]

Confirmed, something is causing the bolt to not cast extra sometimes, this happens on other classes aswell.

XXX Barney