If you read his post with comprehension, you'd notice that he was referring to the leveling phase, before you get mastery.
The reason base damage for elemental's spells is tuned so low is because there are layers upon layers of modifiers tied into every ability, I already linked an article explaining it in detail above, let me do it again:
https://www.stormearthandlava.com/rngsus/
Most people are so fixated on warcraftlogs' graphs and hearsay that they do not understand the real issues that prevent elemental from being a viable spec for progression raiding, which are:
total lack of survivability
no raid utility/immunities
damage VARIANCE that is out of player control