Re the women all working for the major - does Sherlock actually ask them who their employer is, in the courtroom scene, or does he just say it to himself?
Because, if he did ask them directly, why was that not the question that made them log off?
The question that made them log off was "do you have a secret?" and they all said "No!" and went away.
So, if the common thread was that they had all worked for the major, when Sherlock asked "Who's your employer?" why didn't they all disappear then.
Also, if your big secret was that you had previously worked for someone for whom you had signed a confidentiality agreement, would you get all nervous when asked "do you have a secret"? I don't think I would.
I do love Sherlock though and really enjoyed the ep.