Well, for what it's worth here's my experience with spokes. At around 15 stone I have always used DT butted spokes for all my wheel builds, just the normal competition ones (2mm/1.8mm/2mm) and despite my oafish behaviour and downhill/XC MTBing in derbyshire (think of the rock garden at the top of Jacobs ladder, while overtaking all your mates, on a rigid bike!) I have NEVER snapped a spoke. Now contrast this to my recent experience. A factory built set of wheels with plain gauge unbranded black spokes which the rear wheel started to undo itself over the first 50-70 miles of road use before I realised what was happening. I took them back to the shop who backed off and retensioned the wheels so in their words "almost as good as a handbuilt". Over the next few hundred miles I have suffered 4 spoke snappages, this is in a brand new wheel that has only covered around 500 road miles. I know the spokes are cheap unbranded ones but I expect the main problem is fatigue during that initial period of use when the spokes were loose and there must have been a hell of a lot of movement and stress at that time. Now I am paying the price!
I guess raleigh can get away with using 2mm spokes despite the large flange hole clearances as long as everything is nice and tight to prevent the movement/flexing that will cause the spoke failures.
Because of the experience described above and as this is the first time I have had disc brakes I am building my own replacements with a 36 spoke rear and the Alpine III spokes just to be absolutely sure. I think the 36 spokes are overkill and so is the Alpine III spokes but I want to be sure these wheels will still be going strong in 10 years time.
EDIT: I forgot to say, these problematic wheels were a warranty replacement for the originals which had stainless steel spokes and did around 11 months and over 2.5k before the spokes started to pull holes in the rear rim. Nothing wrong with the spokes at all but I have no reason to suspect they were any higher in quality than the black replacements which adds weight to my theory that the looseness caused the subsequent spoke failures on the 'new' wheels. I can't wait to build my own pair then sit back and forget about the whole sorry episode.