Brohan Ironforge not responding appropriately
 

For the Tayla Ironforge quest, the following prompt should work:

You say, 'I will do a favor'

Brohan Ironforge says 'Good. Please find my daughter, Tayla Ironforge. Bring me proof that she is safe. She was last seen somewhere in Neriak. I am a fine blacksmith and I shall give you a worthy gift if you do this for me.'

This works, but is requiring, 'do you a favor'.

Simplified the required text, pending update

Can confirm.

do you a favor works

"I will do you a favor" did not.