I would advise that you wait for the experience letter. DIAC has refused a few visas of late because certain documents were not provided at the time of application and I personally would not risk it, if you can get the letter in a week.
Are you celebrating a birthday in a week that will result in you being able to claim less points against the age criteria?
I am planning to submit my application(175) now but my experience letter latter ( but before 28 days ) since my employer will provide that in next week.I dont want to loose the time and fill my application bcz of my age.
Will that be fine?