I've been using a lot of AEs in group lately to try and keep up with the zerker (hah) and it has become painfully obvious that Self-Combustion's GCD is twice as long as that of any other spell I've ever cast. It's pretty annoying. So what's up with that? Has there ever been a specific reason given for that disparity? I can't recall ever seeing anything about it.
Do you mean the recast timer? Several wizard spells have recast times associated with them. Our stun line, Shocking Vortex, our non-magic instants, Harvests, etc, etc.
No, they mean the global cooldown, exactly as they said. Self-Combustion has a 3 second cooldown where most spells have 1.5 seconds.