PIP assessors

I work as a private advocate, P.A. and Support Worker.
I deal mainly with appeals for DLA,PIP, ESA, Universal Credit and Attendance Allowance( over 65s only) And I am very busy!
I am appalled at the number and types of claims that are a) turned down in the first instance 
b) then get accepted after I have been busy on my clients' behalf 
c) claims that are allegedly "lost" and then re-requested( presumably to check that the responses are still the same.)
c)the number of people - especially but not exclusively, vulnerable, homeless and mental health cases -  who are simply not on the radar of ANY support services ( but are after I've finished with them!)
I have a question about PIP to which I can probably guess the answer:
How can one find out whether the allocated assessor has the correct type of background, training and experience in and of a particular disability or condition?
Take, for example, ADHD, or Autism ( both different in males and females), or fibromyalgia and M.E.?
If one believes that the assessor is NOT competent, presumably one can request someone who IS?
One last thing...how is it legal for landlords and letting agents to specify: NO DSS?
In my professional opinion, this is contravening  the Equality Act 2010 and I am investigatin and challenging every case I come across.

In the meantime, I am happy to assist anyone who needs an experienced brain and a large pair of boots! feel free to contact me!