I have to say my own experience of the ATPLs is that in terms of difficulty they are nothing like as difficult as doing a "proper" degree..... I did an engineering degree that was many times more complex in terms of the level of understanding required than the ATPL exams.... and certainly for my degree there wasn't a question bank in the public domain containing 60-70% of the questions I was likely to face.
I think the 14 GCSE analogy is probably nearer the truth from my own experience.... (without the coursework of course
)... perhaps even less challenging because lets face it the 2 comms exams are not exactly rocket science.
Its really just about volume... nothing too technically difficult if you can get a very basic grip of physics/maths. Like I say it is only my own experience but I managed to get through the ATPLs in 12 months whilst working 60-70 hours per week in a full time job so even the volume side can be done.
Another thing I would point to with the ATPLs is that many many people now seem to be getting through with averages in the 90s for all 14 exams (if the folks I talk to are telling the truth!).... I don't know any other professional exams in which people so regularly get such a high average mark.
Having recently been through the exam process it certainly was not as tough as some people had led me to believe..... good on you though for asking the question, its a big risk.... personally I would never let my parents put their house on the line to fund flying training... many old hands on here spend a lot of time and effort telling wanabees how fickle this industry can be.... why not reduce the risk, get a job and do the exams whilst working if you are that worried about it??