Blizzard has announced that only your highest kill of Sarkareth will give you a chance at the Legendary Evoker Weapon, but it’s very unclear exactly how this works. It’s unclear exactly what this Blue Post means and I think further clarification is needed as many players are asking the following questions due to the ambiguity of the statement:
If you defeat Heroic first, does this mean that you’re locked out of a Mythic chance? Should people killing Mythic Sarkareth not kill Heroic, Normal or LFR before hand? Should people killing Mythic Sarkareth kill LFR > Normal > Heroic in order? Does every difficulty give Evokers 1 roll at the Legendary and killing the boss on a higher difficulty just rolls multiple times? What are the drop chances? Quick update on some discussions we’ve seen -Defeating Scalecommander Sarkareth on the highest difficulty will cover your best chance for getting the Cracked Titan Gem that week. Doing the encounter extra times on lower difficulties won’t increase your chances of getting the item.What this post may be trying to indicate, but explaining poorly, is that each difficulty will have your character roll 1 dice. When you kill Sarkareth at a higher difficulty, it will roll extra times for the uncleared difficulties. As an example, say the drop chance of the Legendary per roll is 0.5 on LFR%, 1% Normal and 2% Heroic (as an example).
This would mean that if you complete Heroic Sarkareth first in a week, you get 3 rolls at each drop meaning you have a chance of getting the Legendary: 3.4651%. If you complete Normal Sarkareth first in a week, you get 2 rolls at the lower two drop chances% meaning you have a chance of getting the Legendary on Normal: 1.495%, then an extra 2% chance when you Read more on wowhead.com