Solly's right - late August to October is when the water is the warmest and therefore the most likely time to see some of the larger pelagics in the South, the time when Oceanics are more likely to be in the area however sightings are, as Solly says, not guaranteed.
If you weren't impressed by Ras Mohamed then either you were taken to the wrong place (or in the wrong direction) at the wrong dive site, or maybe you're looking for something that you can't find here. The Reef here is one of the most impressive in the world, but if its big fish you want, then there are places in the world where you are more likely to get guaranteed sightings. The OWTs are a mystery anyway. Nobody at my centre saw one last year, and I don't recall hearing about them anywhere else in Sharm - and yet they've been quite regular here over the years before - like - a handful of sightings in a season, but fairly regular.
Hope you find what you're looking for with your diving,
Cheers
C.