You asked a honest question and got honest answers.
Of course we all wish you the best of luck, and also hope the caseworker/ECO will give you a chance to rectify your mistake.

We have seen a couple of cases here where missing documents have been requested and subsequently supplied on time and accepted.
The missing documents in both cases turned out to be the Employer letter of confirmation.

Personally, I would not advise applicants to take the same approach.
Visa applications are just too important and costly to mess with and to take unecessary risks, and that's apart from the emotional roller coaster ride.

I think you should begin preparations to secure and supply any and all missing documents as normally the time allowed to submit is often quite short.

By the way your interpretation of the allowable discretion is not quite accurate.

You've said:-
Quote Originally Posted by freyter View Post
...... that they would look at the immigration rules that state if they feel a visa can be approved but that certain documents (like bank statements in a series) are missing then they should request these before refusal....Here's hoping.....
The Financial Requirement actually states:-
...Caseworkers have discretion to rectify minor errors in an otherwise compliant application, e.g. where the applicant has made a simple arithmetical error in adding up properly evidenced figures in the application form, or where the application would meet the financial requirement except that a piece of specified evidence is missing (e.g. one bank statement in a series) and contact with the applicant establishes that this can be submitted quickly. If the applicant fails to send the specified document(s) within the requested time period, the application will fall for refusal.
Semantics I know, but UKBA are known to work in that way.

Hopefully not in your case

Good luck