Why no further Echo on T9?

[Alkimi]

The dps required for 3 meteors is around 2000. But it's harder to hit that mark in T9 due to the downtime between jumps, but there was a 10% echo to help with that.

the dps required to beat Turn 10 without hitting the soft enrage is a little over 2000.

You are the one who's wrong.

It's around 2050 to kill it with a couple of seconds before enrage. However Meteor on 4 adds (around 65-80k damage depending on your party's weapons) contributes a hefty chunk to the party's overall dps.

Also bear in mind that most people solo tank T9. Nothing in final coil can be solo tanked.