EB damage seems bugged. I'm getting lower values than I should according to both wiki and ingame feat description.
I did two sample collections, one at level 7-8 (500+ samples) and one at level 11 (200+ samples).
Both samples do not take critical hits or misses into accounts and they skip resistances/immunities. They also skip cases where elemental damage kills the mob so exotic damage doesn't apply.
First sample should have 2d6 (lvl 1) + 3d6 (lvl 7) + 2d6 (eldritch mastery) damage = 7d6 or 7 to 42 range.
Second sample should have 2d6 (lvl 1) + 5d6 (lvl 11) + 2d6 (eldritch mastery) damage = 9d6 or 9 to 54 range.
In reality they both have less.