First concerning the aquisition of medical and denials on the first two levels:
If a claimant submits their own medical and it contains the required documentation that shows that the claimant meets the listings the wait is VERY short. If most people had the time they'd be way ahead to just go to all their sources and get the medical to submit with their claims.
Also on people over the age of 55 who cannot do their past work it is VERY important that they fill out the report of the jobs they did and all of their duties as fully as possible. If a person does not meet the listings and they are over 55 there are special rules that allow DDS to sometimes allow these people if they do not have any transferable skills to a lighter work are over 55.
However say the disability caseworker requests the info and it takes the persons treating source 2 months to send the info in. Then it is nothing but illegible hand written scribbles. Then the examiner must schedule an exam. It can take anywhere from a few weeks to a month to get a date and then a few weeks to a month (or more) to get the source to send the report to DDS. Then it has to undergo medical review which can take a few days to a few months depending on the examiners caseload and the backlog for for the medical consultants who review them.
Also there is some evidence like heart catherizations, school records or psych treatment records to back up mental allegations that are impossible for SS to buy exams to replace and it can take months sometimes to cajole these sources into responding.
As far as the backlog for ALJ hearings there has always been a backlog. More judges are a first step. However the same thing that makes that process slow makes it more favorable to the claimant.
The rules that the DDS examiners and doctors who review the claims under are very strict. Also they make it harder to allow a claimant who perhaps has multiple severe impairments, but these impairments by themselves do not meet any specific listing. Also after the decision cases adjudicated by the DDS are subject to both an internal QA review and a federal regional quality review where "iffy" cases may be kicked back for more documentation or a reversal of decision. In addition those processing cases at the DDS level are under pretty tight production and mean processing time quotas.
By contrast the ALJ's are not held to as strict production or processing time standards. Also while some of their decisions are reviewed by the Appeals Council there is not the oversight on their decisions that the cases in the DDS receive, and they use this along with the extra time they have due to the lack of strict production standards to often interpret the law in such ways that they allow people that the DDS would never be able to allow with out their QA kicking them back.
Also remember that just a diagnosis is not enough to be allowed on. Most of the disability regulations in SSA's listing of Impairments have criteria that relates to functioning that must be met. A lot of times doctors do not fully address this in their reports. Besides getting your medical records to submit often it is helpful to get your doctor to write a letter on your behalf laying out in detail the things your condition prevents you from doing mentioning the physical findings to support it.
If you want to make sure you get the proper info related to your impairment that DDS needs on the first two levels you can go to the Listings of Impairments on the SSA website and it has the criteria for being found disabled that SSA uses.
http://www.socialsecurity.gov/disability/professionals/bluebook/AdultListings.htmRemember at least at the DDS levels there is less paperwork involved in allowing a claim than denying one so most people working claims will be looking to see if there is any way the claimants case can be allowed. It won't hurt after you have filed your claim to call your worker and ask if there is anything they might need that might help your claim that you could go get.
Hope this helps.