coolas no I don't think that my experience is a particularly bad one, from the other people I know who have children with Specific Learning Difficulties in state and private schools and what I read on mumsnet (far from representative I know ) it is a fairly average experience.
It was a very positive one from the point of view that at my DDs primary she had a brilliant SEN who spotted the problem from the first difficulties with literacy and started intensive targeted intervention at 6 that got her up to average level in reading spelling and writing (albeit she is very slow, tenth percentile). She still thanks that teacher on a almost daily basis for all the tools she gave her then, but that was a rare experience amongst the children with SpLDs I know. Since then though it has been the usual mixture of teachers who really got her and those who tried to fit her into pigeon holes or were completely ignorant (one English teacher pronounced her "cured") I am sorry if I am overreacting to your pronouncement that no one comes back from a private Dyslexia assessment without a diagnosis but I have heard that one a few times usually followed by further unhelpful comments manifesting the stereotype that this is another pushy parent pushing for advantage, including once "she is just like an over exuberant puppy falling over herself all the time and putting her foot in it" ( she is also dyspraxic) the problem is that what this leaves me with is a DD who knows she is bright, and has the confidence to work hard for what she wants to achieve but has little confidence that the rest of the world will understand that.
I can only assume the EP reports you see are nothing like my DDs. They have been absolutely invaluable, both in helping my DD to understand her strengths and weaknesses and in giving signposts to how to support her. The teacher assessor report was not particularly but it was only an update. Those teachers who get her are the ones who have taken the bother to read her reports and then give guidance on her work that is actionable for her. Another bit of luck was having a sixth form tutor who is herself dyslexic and has spent hours with her helping with essay writing skills and mind mapping etc. Yes it has set in place her extra time in exams, but her problems are "moderately severe" and yet she was borderline under the new regs. However their real value has been in her personal and educational development.
I am dyslexic myself, I have achieved two Masters degrees and a long career as a senior manager and yet I can never shake off the belief I am just not that clever, my DDs at least know that is not the case.