Dbat, both of my older two daughters have been trialled on ADHD medication. One is HG+ and we thought had innattentive ADHD but did not feel had any other LDs, and did not suspect ASD in any of it's forms. Medication works in the classic "magic switch" manner for her, there are multiple easily measurably differences in her. She's MORE herself, not less, more creative, engaged, more everything. She wants to take her medication, wants to take it every day and for it to last all day. It's not 100% side effect free but it's very clear, for now, that medication is worthwhile for her.
My older daughter, who is somewhere between bright and MG (variable IQ test response), and clearly has multiple LDs and some combination of ADHD/ASD did not have nearly such a clear response and after a decent trial we stopped medication as there seemed no point in giving a fairly serious medication for no definitive gain, from our perspective or hers. It is possible she had some mild improvements of the sort you are worried would show up in any child, but it was a completely different ball game to her sister.
I tend to agree with you that the medication trial should come after a clear diagnosis of what is wrong. But I have to say that my eldest daughter is an onion that no-one has found easy to peel. She's got a little bit of everything going on, when I say little I mean "almost diagnosable, or just barely diagnosable levels", but is not absolutely clearly any one thing. So despite having seen what seems like every possible person we could trott her out to see she did in fact trial medication before we came to any final conclusions (we still aren't there although Aspergers is now looking likely).
