Optimal time to do FG content

For a first character and in veteran difficulty what is the best time to start doing the FG content?

best storywise= after Ashes of Malmouth
best for fun and challenge= after warden krieg


Elaborating a little:

The FG content is very challenging – but not unfair – when played right after the Warden on Veteran.

But some NPCs in pre-AoM areas have odd behaviors/words when you knowk out FG that early.