I wanna see the guy manage all the characters at once, fluently.
I am certainly no expert on this, but I have read about the subject purely from interest from a technical standpoint. The way it works is the person has to carefully set up macros for each char/account, bind them to keys, then use a 3rd party program to manage the input. Blizzard has made it clear that while automating gameplay fully is illegal, simply using 3rd party tools/add ons to clone signals created by a real person at the controls, and sending to multiple instances, is legal. In practice it really doesn't work at all like independent minds adapting to a situation and adjusting, and the more instances going at the same time, the easier it can get messed up especially in combat formation. Having said that, it requires a good memory on the part of the person doing the controls because they must be able to quickly recall the key bindings they have created for each class, and coordinate it all. Planned out carefully, and I have no doubt a frea- uh I mean determined indivdual who would go to such extremes would spend a great deal of time planning, I am sure the end result is a decently functional if not stellar performing raid/group system.
He may have 36 accounts to maximize classes & templates to switch out easier but I really don't know why he would need to have more than 25 active at a time for raids as that is the group limit on most of the ones people bother with now (old ones have 40 max). Since to stay "legal" he needs to be supplying all the input, unless he is running the same raid instance on multiple realms in which case his input would coordinate properly for them all, it wouldn't seem workable to have them all running simultaneously.
-Skylark