BGG
What assumptions are the human error stat used in the fault trees based upon. It seems logical that it is based upon an average level of training and competence rather than the average number of keystroke errors a secretary makes. When I have looked at fault trees, the human error case is considered in many accident chains. If this assumption is invalidated because of lack of flying hours then the safety case also becomes unravelled.
I agree with Safeware, and the above. It may help if you were to seek out the "Safety Case Policy" manuals from various Aircraft Design Authorities e.g. Westland, BAeS. They are prepared for and used by the DA but, obviously, they meet MoD and CAA requirements and MoD call them up in contracts (or did, in the days when Safety Cases were routinely maintained). Regarding your specific question, the version I have to hand, covering both MoD and CAA, uses this phrase;
".....using emergency procedures but without requiring exceptional pilot skill or strength"
which, I think, tends to confirm your assessment of what skills are assumed. It also confirms the assumption of adequate training is a fundamental component of the Safety Case and, hence, the RTS. If training / currency is compromised, so too is the Safety Case and the Master Airworthiness Reference.
I'm afraid I don't know where it is laid down what the flying hours per pilot are, for any given aircraft; someone like me would be more concerned with Fleet Flying Rate, which is stated in the annual EP Assumptions. (Or not, as the case may be. MoD stopped doing this a couple of years after introducing the policy not to routinely maintain airworthiness - 1991. As the funding was denied for the latter, there was no longer any point providing the annual data used to work out how much funding was needed!). Pilot hours is not quite as simple as dividing the Fleet hours by number of pilots, but it would be a rough guide.