Maybe it's time to hire a diagnostics firm/freelancer or MySQL programmer for a few hours/days to fix this issue? I'm sure the money spent on this expert will be made up from keeping lots of subscribers who might be fed up with the slow loads, and all the new users who will never give the site a chance because of it.
This is not meant as an insult to anyone, but the slowness of the site is killing my desire (and likely others) to visit EN World.
From a commercial standpoint with 4E just recently release, this is the time when EN World should be a smooth as possible to attract new users. These new users, and users of old, are being scared off by the slow loads. Two of my friends who have just started playing D&D with the new edition, couldn't even get the site to load (or they were impatient, but the fact is now they aren't going back).
As MM wrote, as much effort as he puts into this place, it might be beyond his skills as he isn't a database programmer (but your efforts are very much appreciated, MM, and I think you've done so much good for EN World).